fix: Standardize color utils and speaker session UI, timezone

[iamareebjamal]

• Refactor all color utils in one place
• Adjust threshold for switching colors
• Deduplicate color helpers
• Make session list UI in speakers aligned with global UI
• Correct timezone being used in session list in speakers

Fixes #4846

Before:

After:

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/eventyay/open-event-frontend/bjptky66c
✅ Preview: https://open-event-frontend-git-fork-iamareebjamal-color-refactor.eventyay.vercel.app

[niranjan94]

Here is an overview of what got changed by this pull request:

Complexity decreasing per file
==============================
+ app/utils/color.ts  -1
         

See the complete overview on Codacy

[mariobehling]

Very good attention to detail. Thanks!