Correct anything over 20mm I believe bolts straight to the hub, then the wheel to the spacer with original bolts. For anything upto 15mm you need extended bolts to go through the wheel, the spacer and into the hub.
As for the colour, I don't really notice but you could always spray them black before hand.
I'd say any extension of the original OE parts can cause excessive wear but it's a risk you take with any modifications. We'll see after a few 100 miles now when I check to make sure they are still torque'd up....need to wirebrush and paint my callipers anyway