25701 standardize text colors

What does this MR do?

Standardizes text colors, removes unnecessary variables, uses rgba

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Primary color is now rgba (0, 0, 0, .85)

Secondary color is now rgba (0, 0, 0, .55)

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #25701 (closed)