Sorry for the question, but I am not able to find out how to change the color of the states of the covers . As far as I can remember there was a change somewhen the last month, but I can’t find it anymore.
After the breaking change, I used the rgb state color for cover entities, which was working fine until the February core update.
I then changed the theme variable according to the state domain colors, and all is working again. See here for color rules, which includes an example for cover states, too:
Thanks a lot! Thats it!