(similar issue as bug 1401085 again) Steps to Reproduce: 1. run Nightly 58.0a1 (2017-11-06) (64-bit) with clean profile 2. start customize 3. set to Compact Density 4. finish customize Actual result: while customizing, both arrows have same color after customizing, forward arrow is darker Expected result: both arrows has same color always (note that there's no history and both arrows are disabled) actually the same color difference applies on Normal Density, but it's nor obvious on Compact Density, since there's no circle on back arrow. also, the color difference also happens on Dark theme, with inverted brightness.