Theme updates (#12373)

* remove hideous and ugly themes

* incorporate dei into ui design

* neutral as a theme color

* high contrast theme adjustments

* color tweaks

web/tailwind.config.js

@@ -103,6 +103,12 @@ module.exports = {
         audio_review: {
           DEFAULT: "hsl(var(--audio_review))",
         },
+        neutral: {
+          DEFAULT: "hsl(var(--neutral))",
+        },
+        neutral_variant: {
+          DEFAULT: "hsl(var(--neutral_variant))",
+        },
       },
       keyframes: {
         "accordion-down": {