yeah, I don't know either. Maybe it spontaneously decided to invert colors, and I just imagine it coincided with me pressing something. But always my tabs were light gray with black text, like all the other toolbars, urlbars, status bars etc. and then suddenly all tabs but the active one are dark gray with white text.

I can see why someone might like to have this color scheme (except in the sticky tabs it's now hard to see the color change that shows that new emails arrived in my gmail), but I want the light gray back.