what color should I paint my suspension?

I would shy away from powder coat as it is a common problem in the 4x4 world that powder coated pieces often rust from inside the coating with no signs of the corrosion. Paints and primers although not as durable as powder coating have chemical rust inhibitors that powder coating does not. Now if you only drive your car acasionally and only on nice dry sunny days then PC would be fine. This is just my 2 cents, but I have seen first hand rusted out tube bumpers where the Powder coat looked good but the steel was all but gone.