Well there have been some good comments from medical professionals more qualified than I as a Paramedic, but I will second the idea that the possibility of a little paint winding up in a wound is really very secondary to the advantage of seeing the prop arc. Also as has been pointed out, that idea is your Doc's opinion and it doesn't necessarily mean it's everyone else in the medical profession's opinion.

Suggesting that manufacturers be tagged with coloring the tips as a safety issue is just more fodder for the legal profession and they're out of control anyway.

I will add that I have substantial experience as a licensed A&P mechanic with full scale props. The FAA mandates that those props have contrasting color tips which is accomplished by painting the tips. Maybe you could get them to drop that requirement for your noted reasons, or force the full scale manufacturers to provide pre-colored tips while you've working on APC...