Establishing our color perspective

We should create a perspective around color use in GitLab. We can establish what colors are needed, and how we think about them. In general, we should stay focused on a small set of unique colors, and use css formulas to generate the shades and tints needed for various interactions.

@cperessini put together this great visual of the colors that currently exist in our variables.scss. This is a great starting point.

Things to consider:

Accessibility concerns with color blindness
Ensuring proper contrast ratios
Relationship to colors used on Marketing pages
Using grey (and other colors) as background - currently we may rely on grey backgrounds too much