here's the tip i gave to TraXXion..
if u want coloured rims on ur cars, just go to the materials panel, choose the rims one (usually id4 on the list), click on the little "M" box next to Reflect and edit the 2 colours u see on top..
for black rims i just changed grey to black, and white to grey, depending how dark u want ur reflections..
for gold rims i replaced grey with: R,G,B=172,154,82