Adjust contrast for GitOps and Crossplan panels

[andreaskienle]

This came up in our review (@reshnm)

Check the contrast of the GitOps and Crossplane panels. They are hard to read, especially in dark mode.

Is there a set colour code for these, or did we just pick the colours randomly?
Might make sense to align the colours with the graph of #120

Acceptance criteria

• remove colors
• create followup issue for designer round