Trigger a macro based on cell colour change

Not directly. If a cell changes its value, you can capture the

Worksheet_Change

event to trigger a macro. But changing a cell color (or any other aspect of its formatting) does not cause this or any other event to occur.

A rather convoluted way to to this would be to create an array to record the cell colors in VBA, and capture the Select event. Every time a cell is selected you would compare all cell colors to the ones in the array to see if anything changed.