Agree with everything above. Personally I’d go with the neutered silver look on a red (also a red owner). IMO, dark colors is a bit too racy/ricy on the Mz5 and I think it goes better on a car with hard lines, not banged up curves like the 2nd gen. I will leave it to the design of the rim to make it stand out, not the color. I have a set of silver BBS RK1s and didn’t like them test fitted on my previous silver Mz5; they blended in way too much. Look forward to fixing them for the cooper red.
Funny you mention (neon) green! Looking at the color wheel, green (granted not neon) is the complementary color to red. I think you can rock hunter green (j/k). Cooper or bronze would look nice on red, I think.