My car is red, would i need SMR for a dark or light car?

Dark. Mugello is the non-clearcoated right and Hellrot is clearcoated...I think.

I would say light, but it doesn't really matter, the only difference between them is the color of the SMR anyway, they are chemically the same. 3M makes the two kinds as a convenience so if you miss any of the residue etc, it won't stand out so much.