Adjust wave colors on dark theme

Choose colors for better contrast with Adwaita-dark.

Closes #100 (closed)

Preview:

I'm confused about one thing though: If I understand it right the first value (80,80,80) should be chosen if dark theme is set, and the second one should be chosen if the regular theme is set. However when I tested it, the color were only adapted when I used the code like shown here. Is this some more flatpak magic or is this actually correct?

Please give feedback whether I should actually exchange the two values like I think it should be.