Improve readability of colors in light and dark mode

[medeotl]

In light theme (default) we can improve the contrast of green labels (on white background). With a darker green they could be more visibible. On the other hands, the same apply on dark them with red labels (I suggest a lighter red)

Pls take a look at inlcuded screenshots for comparison

Tested on Fedora 37 - Gnome - Wayland - Adwaita theme