diff --git a/src/sass/_colors.scss b/src/sass/_colors.scss
index 8cef13bc..19faa31b 100644
--- a/src/sass/_colors.scss
+++ b/src/sass/_colors.scss
@@ -122,7 +122,7 @@ $link_color:                        if($scheme == 'nord', #5e81ac, #3484e2);
 $link_visited_color:                if($variant == 'light', lighten($text_color, 10%), darken($text_color, 15%));
 
 // Theme colors
-$selection_mode_bg:                 lighten($selected_bg_color, 15%);
+$selection_mode_bg:                 gtkmix(white, $selected_bg_color, 25%);
 $warning_color:                     if($scheme == 'nord', $nord_color_orange, $theme_color_orange);
 $error_color:                       if($scheme == 'nord', $nord_color_red, $theme_color_red);
 $success_color:                     if($scheme == 'nord', $nord_color_green, $theme_color_green);
@@ -273,7 +273,7 @@ $dash_bg:                           if($variant == 'light', rgba(#d1d1d1, $panel
 $entry_bg:                          gtkalpha(currentColor, 0.05);
 $entry_shell_bg:                    gtkalpha(currentColor, 0.1);
 $entry_border:                      $borders_color;
-$entry_highlight:                   rgba($selection_mode_bg, 0.75);
+$entry_highlight:                   gtkalpha($selection_mode_bg, 0.75);
 
 // Button colors
 $button_bg:                         if($variant == 'light', white, #656565);
diff --git a/src/sass/gtk/_colors-libadwaita.scss b/src/sass/gtk/_colors-libadwaita.scss
index fbb6f338..43a58dea 100644
--- a/src/sass/gtk/_colors-libadwaita.scss
+++ b/src/sass/gtk/_colors-libadwaita.scss
@@ -247,12 +247,11 @@ $dark_5: #000000;
     --accent-fg-color: @accent_fg_color;
   }
 
-  $selected_bg_color: var(--accent-bg-color);
-  $primary_color: var(--accent-bg-color);
-  $entry_highlight: RGB(color-mix(in srgb, white 25%, var(--accent-bg-color)), 75%);
-  $progress_color: var(--accent-bg-color);
-  $selection_mode_bg: color-mix(in srgb, white 25%, var(--accent-bg-color));
-  $selected_borders_color:  color-mix(in srgb, black 25%, var(--accent-bg-color));
+  $selected_bg_color: gtkcolor(accent_bg_color);
+  $primary_color: gtkcolor(accent_bg_color);
+  $progress_color: gtkcolor(accent_bg_color);
+  $selection_mode_bg: color-mix(in srgb, white 25%, gtkcolor(accent_bg_color));
+  $entry_highlight: color-mix(in srgb, gtkcolor(window_bg_color) 25%, $selection_mode_bg);
 
   $bg_color: gtkcolor(window_bg_color);
   $base_color: gtkcolor(view_bg_color);
diff --git a/src/sass/gtk/_common-3.0.scss b/src/sass/gtk/_common-3.0.scss
index 564d7ce1..1cdc2c49 100644
--- a/src/sass/gtk/_common-3.0.scss
+++ b/src/sass/gtk/_common-3.0.scss
@@ -248,7 +248,7 @@ $maximized_radius_style: 0 0 $maximized_radius $maximized_radius;
 
   &.csd {
     border-radius: $background_radius_style; // Set csd windows botttom border radius
-    background-color: rgba($bg_color, 0.999);
+    background-color: gtkalpha($bg_color, 0.999);
 
     &.maximized, &.tiled, &.fullscreen {
       border-radius: $maximized_radius_style; // Set csd windows botttom border radius
@@ -1220,7 +1220,7 @@ combobox {
 
   button.combo:disabled arrow,
   button.combo:backdrop arrow {
-    background-color: if($variant == 'light', rgba($text_color, 0.45), gtkmix(white, $button_bg, 25%));
+    background-color: if($variant == 'light', gtkalpha($text_color, 0.45), gtkmix(white, $button_bg, 25%));
   }
 
   decoration,
@@ -1730,7 +1730,7 @@ headerbar {
   &.selection-mode {
     color: $light_fg_color;
     background-color: $selection_mode_bg;
-    border-color: darken($selection_mode_bg, 4%);
+    border-color: gtkmix(black, $selection_mode_bg, 6%);
     box-shadow: none;
     background-image: none;
     text-shadow: none;
@@ -1738,7 +1738,7 @@ headerbar {
     &:backdrop {
       background-color: $selection_mode_bg;
       color: transparentize($light_fg_color, 0.4);
-      border-color: darken($selection_mode_bg, 4%);
+      border-color: gtkmix(black, $selection_mode_bg, 6%);
     }
 
     button:not(.flat):not(.suggested-action):not(.destructive-action):not(.titlebutton):not(.combo) {
@@ -2021,7 +2021,7 @@ treeview.view {
   &:selected {
     border-radius: 0;
     border-left-color: gtkmix($selected_fg_color, $selected_bg_color, 50%);
-    border-top-color: rgba($fg_color, 0.15); // doesn't work unfortunately
+    border-top-color: gtkalpha($fg_color, 0.15); // doesn't work unfortunately
     background-color: $selected_bg_color;
     color: $selected_fg_color;
 
@@ -2128,12 +2128,12 @@ treeview.view {
 
       &:hover {
         color: $fg_color;
-        background-color: rgba($fg_color, 0.06);
+        background-color: gtkalpha($fg_color, 0.06);
       }
 
       &:active {
         color: $fg_color;
-        background-color: rgba($fg_color, 0.1);
+        background-color: gtkalpha($fg_color, 0.1);
       }
 
       &:disabled {
@@ -2321,7 +2321,7 @@ menu {
       -gtk-icon-source: -gtk-icontheme('pan-down-symbolic');
     }
 
-    &:hover { background-color: rgba($fg_color, 0.08); }
+    &:hover { background-color: gtkalpha($fg_color, 0.08); }
 
     &:disabled {
       color: transparent;
@@ -2436,12 +2436,12 @@ cursor-handle {
 
   &:hover:not(:checked) {
     color: gtkmix($fg_color, $disabled_fg_color, 50%);
-    background-color: rgba($fg_color, 0.06);
+    background-color: gtkalpha($fg_color, 0.06);
   }
 
   &:checked {
     color: $fg_color;
-    background-color: rgba($fg_color, 0.12);
+    background-color: gtkalpha($fg_color, 0.12);
   }
 }
 
@@ -2645,12 +2645,12 @@ notebook {
 
         &:hover {
           color: $fg_color;
-          background-color: rgba($fg_color, 0.1);
+          background-color: gtkalpha($fg_color, 0.1);
         }
 
         &:active {
           color: if($variant == 'light', darken($fg_color, 10%), lighten($fg_color, 10%));
-          background-color: rgba($fg_color, 0.2);
+          background-color: gtkalpha($fg_color, 0.2);
         }
       }
     }
@@ -2754,10 +2754,10 @@ scrollbar {
 // Switches
 //
 
-$switch_image: linear-gradient(0deg, rgba($fg_color, 0.25) 0%, rgba($fg_color, 0.35) 100%);
-$switch_disabled_image: linear-gradient(0deg, rgba($fg_color, 0.1) 0%, rgba($fg_color, 0.15) 100%);
+$switch_image: linear-gradient(0deg, gtkalpha($fg_color, 0.25) 0%, gtkalpha($fg_color, 0.35) 100%);
+$switch_disabled_image: linear-gradient(0deg, gtkalpha($fg_color, 0.1) 0%, gtkalpha($fg_color, 0.15) 100%);
 $switch_checked_image: linear-gradient(0deg, lighten($selected_bg_color, 10%) 0%, $selected_bg_color 100%);
-$switch_checked_backdrop_image: linear-gradient(0deg, rgba($fg_color, 0.45) 0%, rgba($fg_color, 0.55) 100%);
+$switch_checked_backdrop_image: linear-gradient(0deg, gtkalpha($fg_color, 0.45) 0%, gtkalpha($fg_color, 0.55) 100%);
 $switch_checked_disabled_image: linear-gradient(0deg, lighten($selected_bg_color, 35%) 0%, lighten($selected_bg_color, 25%) 100%);
 $switch_animation: switch_ripple_effect 0.3s cubic-bezier(0, 0, 0.2, 1);
 
@@ -2770,8 +2770,8 @@ $switch_animation: switch_ripple_effect 0.3s cubic-bezier(0, 0, 0.2, 1);
 
   to {
     background-image: $switch_checked_image, radial-gradient(circle farthest-corner at center,
-                                      rgba($selected_bg_color, 0.75) 100%,
-                                      rgba($selected_bg_color, 0.0) 0%);
+                                      gtkalpha($selected_bg_color, 0.75) 100%,
+                                      gtkalpha($selected_bg_color, 0.0) 0%);
   }
 }
 
@@ -2799,7 +2799,7 @@ switch {
     color: transparent;
     box-shadow: inset 0 1px 2px rgba(black, 0.15);
     transition: background-image 0.3s, box-shadow 0;
-    background-image: $switch_checked_image, radial-gradient(circle farthest-corner at center, rgba($selected_bg_color, 0.75) 100%, transparent 0%);
+    background-image: $switch_checked_image, radial-gradient(circle farthest-corner at center, gtkalpha($selected_bg_color, 0.75) 100%, transparent 0%);
 
     &:disabled {
       background-color: transparent;
@@ -3040,7 +3040,7 @@ scale {
     border-radius: $bt_radius;
     background-color: $_scale_trough_bg;
 
-    &:disabled { background-color: rgba($_scale_trough_bg, 0.12); }
+    &:disabled { background-color: gtkalpha($_scale_trough_bg, 0.12); }
 
     //OSD troughs
     .osd & {
@@ -3085,7 +3085,7 @@ scale {
   }
 
   slider {
-    $_slider_border: rgba($fg_color, 0.15);
+    $_slider_border: $borders_color;
 
     background-color: $selected_fg_color;
     border: 1px solid $_slider_border;
@@ -3109,7 +3109,6 @@ scale {
 
     &:disabled {
       background-color: darken($selected_fg_color, 5%);
-      border-color: darken($_slider_border, 5%);
     }
 
     // Selected list-row and infobar sliders
@@ -3573,7 +3572,7 @@ row {
   padding: $container_padding;
   margin: 6px 20px 24px 20px;
   color: $fg_color;
-  background-color: rgba($header_bg, 0.85);
+  background-color: gtkalpha($header_bg, 0.85);
   // background-image: linear-gradient(0deg, $bg_color 0%, $bg_color 85%, darken($bg_color, 5%) 95%, darken($bg_color, 15%) 100%);
   border-radius: $wm_radius;
   border: none;
@@ -3639,29 +3638,29 @@ calendar {
   &.button {
     @extend %undecorated_button;
 
-    color: rgba($fg_color, 0.45);
+    color: gtkalpha($fg_color, 0.45);
 
     &:hover { color: $fg_color; }
 
     &:disabled { color: $disabled_fg_color; }
   }
 
-  &:indeterminate { color: rgba($fg_color, 0.55); }
-  &.highlight { color: rgba($fg_color, 0.65); font-weight: 500; }
+  &:indeterminate { color: gtkalpha($fg_color, 0.55); }
+  &.highlight { color: gtkalpha($fg_color, 0.65); font-weight: 500; }
 }
 
 //
 // Dialogs
 //
 
-$messagedialog_bg: if($trans == 'true', rgba($bg_color, 0.98), $bg_color);
+$messagedialog_bg: if($trans == 'true', gtkalpha($bg_color, 0.98), $bg_color);
 
 messagedialog { // Message Dialog styling
-  &.background { background-color: rgba($messagedialog_bg, 1); }
+  &.background { background-color: gtkalpha($messagedialog_bg, 1); }
 
   .titlebar {
     min-height: 28px;
-    background-color: rgba($messagedialog_bg, 1);
+    background-color: gtkalpha($messagedialog_bg, 1);
     border: none;
   }
 
@@ -3924,13 +3923,13 @@ placessidebar {
 
     &:drop(active):not(:disabled) {
       box-shadow: none;
-      background-color: rgba($drop_target_color, 0.15);
+      background-color: gtkalpha($drop_target_color, 0.15);
 
       &, label, image { color: $drop_target_color; }
 
       &:selected {
         &, label, image { color: $drop_target_color; }
-        background-color: rgba($drop_target_color, 0.35);
+        background-color: gtkalpha($drop_target_color, 0.35);
       }
     }
   }
diff --git a/src/sass/gtk/_common-4.0.scss b/src/sass/gtk/_common-4.0.scss
index 0eee3a33..7ec02bb9 100644
--- a/src/sass/gtk/_common-4.0.scss
+++ b/src/sass/gtk/_common-4.0.scss
@@ -525,7 +525,7 @@ spinner {
   @include entry(normal);
   border: none;
 
-  &:focus {
+  &:focus-within {
     @include entry(focus);
   }
 
@@ -2225,7 +2225,7 @@ headerbar {
     text-shadow: none;
 
     @if $gnome_version == 'old' {
-      border-color: darken($selection_mode_bg, 5%);
+      border-color: gtkmix(black, $selection_mode_bg, 6%);
     } @else {
       border-color: color-mix(in srgb, black 15%, $selection_mode_bg)
     }
@@ -2235,7 +2235,7 @@ headerbar {
       color: gtkalpha($light_fg_color, 0.6);
 
       @if $gnome_version == 'old' {
-        border-color: darken($selection_mode_bg, 5%);
+        border-color: gtkmix(black, $selection_mode_bg, 6%);
       } @else {
         border-color: color-mix(in srgb, black 15%, $selection_mode_bg)
       }
diff --git a/src/sass/gtk/_drawing-3.0.scss b/src/sass/gtk/_drawing-3.0.scss
index cd685c4c..9f90585f 100644
--- a/src/sass/gtk/_drawing-3.0.scss
+++ b/src/sass/gtk/_drawing-3.0.scss
@@ -106,7 +106,7 @@
   //
     color: $selected_fg_color;
     background-color: $selected_bg_color;
-    border-color: darken($selection_mode_bg, 5%);
+    border-color: gtkmix(black, $selected_bg_color, 8%);
   }
 
   @else if $t==osd-insensitive {
diff --git a/src/sass/gtk/_drawing-4.0.scss b/src/sass/gtk/_drawing-4.0.scss
index ed8ed18d..15464f5f 100644
--- a/src/sass/gtk/_drawing-4.0.scss
+++ b/src/sass/gtk/_drawing-4.0.scss
@@ -47,7 +47,7 @@
   // insensitive entry
   //
     color: $disabled_fg_color;
-    background-color: gtkalpha($entry_bg, 0.02);
+    background-color: $entry_bg;
   }
 
   @if $t==header-normal {
@@ -108,7 +108,7 @@
     background-color: $selected_bg_color;
 
     @if $gnome_version == 'old' {
-      border-color: darken($selection_mode_bg, 5%);
+      border-color: gtkmix(black, $selected_bg_color, 6%);
     } @else {
       border-color: color-mix(in srgb, black 25%, $selected_bg_color)
     }
diff --git a/src/sass/gtk/apps/_gnome-3.22.scss b/src/sass/gtk/apps/_gnome-3.22.scss
index 4a23c978..eefeea9d 100644
--- a/src/sass/gtk/apps/_gnome-3.22.scss
+++ b/src/sass/gtk/apps/_gnome-3.22.scss
@@ -19,8 +19,8 @@ $nautilus_sidebar_image: image($dark_sidebar_bg);
 @if $nautilus_style == 'stable' {
   $nautilus_sidebar_image: linear-gradient(90deg, $dark_sidebar_bg 0%,
                                                   $dark_sidebar_bg $nautilus_sidebar_size,
-                                                  rgba($dark_sidebar_bg, 0) $nautilus_sidebar_size,
-                                                  rgba($dark_sidebar_bg, 0) 100%);
+                                                  gtkalpha($dark_sidebar_bg, 0) $nautilus_sidebar_size,
+                                                  gtkalpha($dark_sidebar_bg, 0) 100%);
 
   $nautilus_bg_image: linear-gradient(90deg, $dark_sidebar_bg 0%,
                                              $dark_sidebar_bg $nautilus_sidebar_size,
@@ -37,7 +37,7 @@ $nautilus_sidebar_image: image($dark_sidebar_bg);
   $dialog_header_borders_image: linear-gradient(90deg, $dialog_bg_color 0px,
                                                        $header_border 25%);
 
-  $nautilus_actionbar_image: linear-gradient(90deg, rgba($dark_header_bg, 0) 5%,
+  $nautilus_actionbar_image: linear-gradient(90deg, gtkalpha($dark_header_bg, 0) 5%,
                                                     transparentize($dark_header_bg, 0.2) 40%);
 
   $nautilus_actionbar_borders_image: linear-gradient(90deg, transparent 0px,
@@ -207,12 +207,12 @@ $nautilus_sidebar_image: image($dark_sidebar_bg);
           padding: 2px 4px;
 
           &:hover {
-            background-color: rgba($fg_color, 0.1);
+            background-color: gtkalpha($fg_color, 0.1);
           }
 
           &:active, &:active:hover {
             transition: background-color ease-out 200ms;
-            background-color: rgba($fg_color, 0.2);
+            background-color: gtkalpha($fg_color, 0.2);
           }
 
           &:selected.has-open-popup,
@@ -240,14 +240,14 @@ $nautilus_sidebar_image: image($dark_sidebar_bg);
         &:drop(active):not(:disabled) {
           border: none;
           border-radius: 0;
-          background-color: rgba($dark_sidebar_fg, 0.15);
+          background-color: gtkalpha($dark_sidebar_fg, 0.15);
 
           &, label, .sidebar-icon { color: $dark_sidebar_fg; }
 
           &:selected.has-open-popup,
           &:selected, &:selected:hover {
             background-image: none;
-            background-color: rgba($selected_bg_color, 0.15);
+            background-color: gtkalpha($selected_bg_color, 0.15);
             &, label, .sidebar-icon { color: $selected_bg_color; }
           }
         }
@@ -375,16 +375,16 @@ $nautilus_sidebar_image: image($dark_sidebar_bg);
 
       button {
         color: $selection_mode_bg;
-        background-color: rgba($selection_mode_bg, 0.15);
+        background-color: gtkalpha($selection_mode_bg, 0.15);
         border: none;
 
-        &:hover { background-color: rgba($selection_mode_bg, 0.25); }
+        &:hover { background-color: gtkalpha($selection_mode_bg, 0.25); }
         &:active, &:checked { background-color: $selection_mode_bg; color: white; }
         &:disabled {
-          background-color: rgba($selection_mode_bg, 0.05);
-          color: rgba($selection_mode_bg, 0.35);
+          background-color: gtkalpha($selection_mode_bg, 0.05);
+          color: gtkalpha($selection_mode_bg, 0.35);
 
-          label { color: rgba($selection_mode_bg, 0.35); }
+          label { color: gtkalpha($selection_mode_bg, 0.35); }
         }
       }
 
@@ -1082,7 +1082,7 @@ window.org-gnome-Builder.workspace {
 
         &:active, &:checked {
           color: $fg_color;
-          background-color: rgba($fg_color, 0.25);
+          background-color: gtkalpha($fg_color, 0.25);
         }
 
         > box.horizontal > box.horizontal {
@@ -1199,9 +1199,9 @@ widget {
       margin: -1px; // kill ugly borders
 
       row.activatable {
-        color: rgba($fg_color, 0.75);
+        color: gtkalpha($fg_color, 0.75);
         &:hover,
-        &:active { color: rgba($fg_color, 0.75); }
+        &:active { color: gtkalpha($fg_color, 0.75); }
       }
 
       // kill ugly separators
@@ -1225,7 +1225,7 @@ widget {
 }
 
 graph-switcher-button.toggle {
-  color: rgba($fg_color, 0.75);
+  color: gtkalpha($fg_color, 0.75);
   font-weight: 500;
   &:hover { // use opaque
     color: $fg_color;
@@ -1248,7 +1248,7 @@ box.speedometer {
   &-outter { opacity: 0.8; } // reduce alpha for our troughs
 
   &-content-area { // cover up meter troughs with selection colour
-    box-shadow: 0 0 0 4px rgba($selected_bg_color, 0.2);
+    box-shadow: 0 0 0 4px gtkalpha($selected_bg_color, 0.2);
   }
 }
 
@@ -1779,7 +1779,7 @@ window.background.csd {
     }
 
     > overlay > scrolledwindow > viewport.frame {
-      background-color: rgba($base_color, 1);
+      background-color: gtkalpha($base_color, 1);
       border-bottom-right-radius: $wm_radius;
 
       > hdycolumn > stack > box.horizontal > box.vertical > box.horizontal {
@@ -1835,7 +1835,7 @@ headerbar.titlebar.incognito-mode {
 
 // reset inverted foreground colour
 notebook > box > stack > box.vertical > paned.vertical > overlay {
-  > .floating-bar { color: rgba($fg_color, 0.75); }
+  > .floating-bar { color: gtkalpha($fg_color, 0.75); }
 }
 
 // overrides foregrounds for 3.24's ssd-mode
@@ -1872,7 +1872,7 @@ popover.background:not(.emoji-picker) > box.vertical > scrolledwindow {
 
     > row.activatable {
       background-color: if($variant=='light', $bg_color, lighten($bg_color, 10%));
-      color: rgba($fg_color, 0.85);
+      color: gtkalpha($fg_color, 0.85);
       border-radius: $bt_radius;
       border: 1px solid $borders_color;
       margin: 2px;
@@ -1890,14 +1890,14 @@ popover.background:not(.emoji-picker) > box.vertical > stack > box.vertical {
     border: 1px solid $borders_color;
 
     > list.background > row.activatable.bookmarks-row {
-      background-color: rgba($base_color, 0.35);
-      color: rgba($fg_color, 0.85);
+      background-color: gtkalpha($base_color, 0.35);
+      color: gtkalpha($fg_color, 0.85);
       border-bottom: 1px dashed gtkalpha(currentColor, 0.05);
       padding: 6px;
 
       &:hover,
       &:active,
-      &:checked { color: $fg_color; background-color: rgba($fg_color, 0.05); }
+      &:checked { color: $fg_color; background-color: gtkalpha($fg_color, 0.05); }
 
       button.flat {
         min-width: 16px;
@@ -2129,13 +2129,13 @@ stack.view.polari-entry-area {
 
   button.popup.flat.toggle.polari-nick-button {
     &:hover {
-      background-color: rgba($fg_color, 0.15);
+      background-color: gtkalpha($fg_color, 0.15);
       box-shadow: none;
       background-image: none;
     }
 
     &:active, &:checked {
-      background-color: rgba($fg_color, 0.25);
+      background-color: gtkalpha($fg_color, 0.25);
       box-shadow: none;
       background-image: none;
     }
@@ -2390,7 +2390,7 @@ window.background.csd {
     // border-radius: 0 0 $wm_radius $wm_radius;
   }
 
-  .content-view:hover { background-color: rgba($fg_color, 0.08); }
+  .content-view:hover { background-color: gtkalpha($fg_color, 0.08); }
 
   viewport.frame { // Documents
     background-color: transparent;
@@ -2608,12 +2608,12 @@ window#GearyMainWindow.background.csd { // <= 3.32
 
           &:hover {
             color: $fg_color;
-            background-color: rgba($fg_color, 0.1);
+            background-color: gtkalpha($fg_color, 0.1);
           }
 
           &:selected {
             color: $fg_color;
-            background-color: rgba($fg_color, 0.15);
+            background-color: gtkalpha($fg_color, 0.15);
           }
         }
       }
@@ -2629,14 +2629,14 @@ window#GearyMainWindow.background.csd { // <= 3.32
     statusbar {
       margin: -8px -12px;
       border: none;
-      background-color: rgba($dark_sidebar_bg, 1);
+      background-color: gtkalpha($dark_sidebar_bg, 1);
       border-bottom-left-radius: $wm_radius;
 
       frame > border { border: none; }
     }
 
     frame.geary-conversation-frame {
-      background-color: rgba($dark_sidebar_bg, 1);
+      background-color: gtkalpha($dark_sidebar_bg, 1);
 
       > border { border: none; }
 
@@ -2650,10 +2650,10 @@ window#GearyMainWindow.background.csd { // <= 3.32
         treeview.view {
           background-image: none;
 
-          &:hover { background-color: rgba($fg_color, 0.1); }
+          &:hover { background-color: gtkalpha($fg_color, 0.1); }
 
           &:selected {
-            background-color: rgba($fg_color, 0.15);
+            background-color: gtkalpha($fg_color, 0.15);
             color: if($variant == 'light', $fg_color, $selected_fg_color);
           }
 
@@ -2754,15 +2754,15 @@ window#GearyMainWindow.background.csd { // <= 3.32
 
         &:hover {
           color: $fg_color;
-          background-color: rgba($fg_color, 0.1);
+          background-color: gtkalpha($fg_color, 0.1);
         }
 
         &:selected {
           color: $fg_color;
-          background-color: rgba($fg_color, 0.15);
+          background-color: gtkalpha($fg_color, 0.15);
 
           &:hover {
-            background-color: rgba($fg_color, 0.12);
+            background-color: gtkalpha($fg_color, 0.12);
           }
         }
       }
@@ -2785,15 +2785,15 @@ window#GearyMainWindow.background.csd { // <= 3.32
 
         &:hover {
           color: $fg_color;
-          background-color: rgba($fg_color, 0.1);
+          background-color: gtkalpha($fg_color, 0.1);
         }
 
         &:selected {
           color: $fg_color;
-          background-color: rgba($fg_color, 0.15);
+          background-color: gtkalpha($fg_color, 0.15);
 
           &:hover {
-            background-color: rgba($fg_color, 0.12);
+            background-color: gtkalpha($fg_color, 0.12);
           }
         }
       }
@@ -2819,14 +2819,14 @@ window#GearyMainWindow.background.csd { // <= 3.32
         margin: 0 $container_padding / 2;
 
         &:hover {
-          background-color: rgba($fg_color, 0.1);
+          background-color: gtkalpha($fg_color, 0.1);
           border-color: transparent;
         }
 
         &:selected, &:active {
           border-color: transparent;
           border-radius: $mn_radius;
-          background-color: rgba($fg_color, 0.15);
+          background-color: gtkalpha($fg_color, 0.15);
           color: if($variant == 'light', $fg_color, $selected_fg_color);
         }
 
diff --git a/src/sass/gtk/apps/_gnome-40.0.scss b/src/sass/gtk/apps/_gnome-40.0.scss
index 6f210d6e..ed5215c9 100644
--- a/src/sass/gtk/apps/_gnome-40.0.scss
+++ b/src/sass/gtk/apps/_gnome-40.0.scss
@@ -22,7 +22,7 @@ $flap_sidebar_size: 240px;
   $nautilus_header_image: linear-gradient(90deg, transparent ($flap_sidebar_size / 2),
                                                  $dark_header_bg 40%);
 
-  $nautilus_header_borders_image: linear-gradient(90deg, rgba($header_border, 0) (($flap_sidebar_size / 2) - 40px),
+  $nautilus_header_borders_image: linear-gradient(90deg, gtkalpha($header_border, 0) (($flap_sidebar_size / 2) - 40px),
                                                          $header_border 40%);
 }
 
@@ -1155,28 +1155,28 @@ carousel.card {
 
   &.green, &.details-rating-0 {
     color: darken($theme_color_green, 15%);
-    background-color: rgba($theme_color_green, 0.15);
+    background-color: gtkalpha($theme_color_green, 0.15);
   }
 
   &.blue,
   &.details-rating-5 {
     color: $theme_color_blue;
-    background-color: rgba($theme_color_blue, 0.15);
+    background-color: gtkalpha($theme_color_blue, 0.15);
   }
 
   &.yellow, &.details-rating-12 {
     color: darken($theme_color_yellow, 15%);
-    background-color: rgba($theme_color_yellow, 0.15);
+    background-color: gtkalpha($theme_color_yellow, 0.15);
   }
 
   &.details-rating-15 {
     color: $theme_color_orange;
-    background-color: rgba($theme_color_orange, .15);
+    background-color: gtkalpha($theme_color_orange, .15);
   }
 
   &.red, &.details-rating-18 {
     color: darken($theme_color_red, 15%);
-    background-color: rgba($theme_color_red, 0.15);
+    background-color: gtkalpha($theme_color_red, 0.15);
   }
 }