UX: Color contrast

As part of UX FY20-Q1 OKRs we have committed to accomplishing the following:

Improve usability and help beautify our UI by addressing 100% of known color contrast issues and updating CSS according to design system specs.

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In order to accomplish this OKR we will:

• Implement correct colors from https://design.gitlab.com/foundations/colors throughout the product
• Determine if any other major color contrast issues remain after updating colors and address them in separate issues