Is there a preferred color to a rear axle?
 

A there a preferred color for a rear axle? White or light grey seems to be almost standard race car, and I assume to spot leaks? Any suggestions?

It's hard to beat semi gloss black from a spray can for a street car. It will get scuffed up from jack stands and the floor jack so the black is nice because it is easy to touch up with a rattle can. It is also great when you start making changes it comes off easy and you can just touch it up and be on the road.

Yeah, we always painted them white in the race cars so it was easier to spot leaks or cracks.

For most other cars, semi gloss black is the way to go. Unless you have something really fancy under there, I wouldn't want it to draw attention.