Updating palette base color token type for better type safety

[bheston]

Pull Request

Description

Added the palette base colors as css tokens so they are also available in styling. Using a base color directly is not the core use case of the Adaptive UI color model because it does not convey the semantic intent behind a derived color, but there are valid cases for this.

The plumbing requires this to be a Color and not a hex string.

Test Plan

Tested in Designer plugin

Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation for this project.