Firefox Colors represents the whole sad history of Firefox and Mozilla. Starting with the best of intentions, and then like a machine rolling through mud, accumulating sludge as it progresses till it is unrecognisable and impossible to use. Gets a good cleanup and starts all over again.
I agree with many of the others, who, like me, are frustrated at this stupid implementation. Every change appears to be irreversible. I have lost all my careful colour setups of versions past. Oh well, there are probably some idiots in a room somewhere patting themselves on the back and thinking they did a great job - so this won't change.
It's okay, we are almost at the point in the Firefox cycle where I drop off and walk with relief towards Chrome...