Environment info

• Browser, version, OS, platform: See below
• Instance URL: N/A
• Frontend version (see settings -> about): f1910b37
• Backend version (see settings -> about): N/A
• Browser extensions (ublock, rikaichamp etc): None
• Known instance/user customizations (i.e. pleromafe mods/forks, instance styles etc) None

Bug description

Chrome: On a ThemesV2 theme, only clicked/active buttons change color. On ThemesV3 most of the buttons change color regardless of state.

Firefox: Seemingly same behavior as on Chrome using ThemesV3. ThemesV2 and ThemesV3 behave the same on FF.

Issue cropped up after merging !2098 (merged)