I'm in the process of ordering this stuff:

Streetglo - Invisible high intensity white reflective black tape strips kit for black motorcycle frames, bicycles or other vehicles.

I had it before on my Surly LHT fenders and the reflective tape is legit, it looks black like fenders (gloss). When you shine a flashlight on it, it turns bright white (like the 3m reflective tape). If you're looking for something you can use on a something that's black so it matches your gear, this is the stuff to get.

V