[pilcrow]

Changing the colour of an icon part in the mirror doesn't cause your in-world icon to update until something happens that would regenerate it (relogging, saving/reloading the outfit, or adding/removing an icon part, in my experience)

This doesn't affect the actual saved values or the function of the mirror itself (it updates fine in the window), but it does add the slightly pesky step of toggling an icon part on and off to force an update after you've made colour changes.