Improve color system

[kasbah]

This is a tracking issue for improving the color system that we rationalized with #888. Some things to consider:

• We don't need so many grays
• We don't need so many slightly different hovers
• Topos brand colors and "positive" and "negative" colors do not work well together
• CatColab colors should differ from Topos colors but would be nice if they still worked well together. There is a color design for Topos branding that we could possibly riff on.
• We intend to create two tiers in the palette:
  i. Color names like --color-gray-100 --color-blue-100 etc.
  ii. A tier of semantic aliases of the color names to their intended purpose e.g. --color-button-positive-hover