I used Firefox Color to make my browser theme darkish and low contrast, but the color of tag groups was NOT something I was able to alter, and it responded to me darkening of the theme by becoming high-contrast pastel in comparison. I can change the measly few color options listed and they all show up pastel light, which is very annoying when I'm trying to have a low contrast browser because high-contrast light elements give me migraines, I'm getting a migraine right now just from being on this fffffff white webpage. It's obnoxious that the tab group colors insist on being like that in spite of having a feature that's supposed to control the color of the browser!