Recently painted one of these. Was going to just use DP74LF epoxy primer with reducer added to give it a bit of sheen. It came out way too orange in my opinion. I remembered I had some paint from when I was matching drum brake springs and found one that seemed to be a good match to the rear. It's for the little short spring that attaches to the parking brake equalizer bracket between the shoes.
Will post some pics after I get the diff back this weekend. My paint is an acrylic enamel, so it's a proper topcoat, with hardener. I did add a bit of flattening agent so it wouldn't be glossy. Turned out really nice IMHO. :-)