Reaction on mode switch

As soon as the control surface script is selected, I would like the RGB lights on my MF Twister to be arranged in rainbow, for example. However from the list of reaction listeners, it seems that I must "do something" first. So I thought if there is an option like reaction on mode switch that would be perfect.

I know that MF Utility program could set starting LED colors, but their color palette is not as fine grained as I could define in CSS. I would like to use CSS to override and colorize the controller completely.