I've heard if some folks staining them (Rit Dye), that is the preferred method, I believe. But I have painted them black myself, then re-balanced them. It was a spray paint from Krylon made for plastic. Worked fine. Plasti-dip is too thick and heavy, I would assume. Plus it's peel able. Not good, mid flight!
I used this method way back when I was a kid dying nitro rc nylon wheels. It looks cool and doubt it affects the reliability but the only concern I have is when you require warranty work involving a prop failure. Might not be a good idea in that scenario. If your warranty is up why not though.