Minor content adjustments to color page

[nataliafitzgerald]

Minor content adjustments to the text content on color page.

Additions

• Changed "primary palette" to "primary colors"
• Other minor wording tweaks

Removals

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Changes

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Testing

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Review

• @cfarm

Preview this PR without the whitespace changes

Screenshots

Notes

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Todos

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Checklist

• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code can be automatically merged (no conflicts)
• [ ] Code follows the standards laid out in the front end playbook
• [ ] Passes all existing automated tests
• [ ] New functions include new tests
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged
• [ ] Visually tested in supported browsers and devices
• [ ] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[Scotchester]

:+1: