Add GTK theming for everforest

colors/everforest/default.nix

@@ -0,0 +1,15 @@
+{
+  kitty-theme = "Everforest Dark Hard";
+  gtkTheme = pkgs: {
+    package = pkgs.callPackage ./gtk.nix {};
+    name = "Everforest-Dark-BL";
+  };
+  wallpaper = "306286.jpg";
+
+  background = "#1e2326";
+  background-alt = "#272e33";
+  foreground = "#d3c6aa";
+  primary = "#83c092";
+  alert = "#e67e80";
+  disabled = "#2e383c";
+}

colors/everforest/gtk.nix

@@ -0,0 +1,43 @@
+{ lib
+, stdenv
+, fetchFromGitHub
+, gtk-engine-murrine
+, jdupes
+}:
+
+stdenv.mkDerivation rec {
+  pname = "everforest-gtk";
+  version = "unstable-2022-12-09";
+
+  src = fetchFromGitHub {
+    owner = "Fausto-Korpsvart";
+    repo = "Everforest-GTK-Theme";
+    rev = "af5920c8a16a53064cbcb7582bd7ef0ba8f44d83";
+    sha256 = "lIAJN8ljmN4RyvyPpHoAheyQBX/qyGXZsGvoTl1vt50=";
+  };
+
+  sourceRoot = ".";
+
+  nativeBuildInputs = [ jdupes ];
+
+  propagatedUserEnvPkgs = [ gtk-engine-murrine ];
+
+  installPhase = ''
+    runHook preInstall
+
+    mkdir -p $out/share/themes
+
+    cp -a source/themes/* $out/share/themes
+
+    jdupes -L -r $out/share
+
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    description = "Everforest colour palette for GTK";
+    homepage = "https://github.com/Fausto-Korpsvart/Everforest-GTK-Theme";
+    license = licenses.gpl3Only;
+    platforms = platforms.all;
+  };
+}