MD, NJ, NM, NY, ND, SC, & VT all have helmet reflector laws.
Are these laws heavily enforced?
I would kinda doubt it, unless maybe the rider starts playing
roadside attorney or motor mouth.
VT (and it's likely many other states)
requires DOT approved lids. Leaving a DOT
designation on a helmet un-obscured could
be a good method to avoid a pinch.
Reflective tape is also available in black, that reflects white.
http://www.identi-tape.com/eng-sr1.html