add granite grey color

Author: Pliavi

static/styles/settings/color.css

@@ -1,6 +1,7 @@
 :root {
   --color-arsenic: #3a4042;
   --color-arsenic-light: rgba(58, 64, 66, 0.5);
+  --color-granite-grey: #646165;
   --color-old-silver: #828282;
   --color-eggshell: #eae6da;
   --color-eggshell-light: rgba(234, 230, 218, 0.3);