Hotkeys for swapping to previous/next color in palette

[popcar2]

Feature/enhancement description: This feature would be extremely useful and can help me spend less time clicking the menu to swap between colors. Having custom palettes is already excellent, but this could really make things smoother for me.

I would prefer using "," for previous color and "." for next color (since they are < and >, but I wouldn't want to hold shift to use it).

[herrsimon]

Very useful feature! Even better would be to make these proposed (and all other existing keybindings) user configurable.