Masterbar: Update colors so they match Modern (default) color scheme.

[jasmussen]

Related to https://github.com/Automattic/dotcom-forge/issues/8519

Proposed Changes

Updates masterbar colors to match the Modern color scheme, which is the default admin color scheme.

Before

After

Why are these changes being made?

There are color scheme colors from individual site installs, and then global Calypso styles. Over time, colors have drifted out of sync, likely as default admin color schemes have been updated, and changed.

This PR fixes issues with the Modern color scheme (there was a contrast issue with the unread bell), and syncs up the color schemes applied to Calypso (Reader, Me, Sites) so they match the default Modern color scheme.

That specifically includes updating the grays. The default shades of gray in the WordPress design system (as defined here) are not yet in Color Studio, and must therefore be defined inline. CC: @Automattic/dotcom-design

Testing Instructions

Apply the PR, then test the wp-admin sections, such as Users > Profile, as well as Reader, Me, and Sites, to see if the colors of the adminbar/masterbar match.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-130158

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-130158&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-130158&env=a8c-for-agencies

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.