I used to have black rats that were pets, many years before I got into snakes, & yes, I've bred not only "hooded" but all black or gray rats too. Domestic rats
come in other colors besides white...they can also be a pretty beige/tan or agouti (a mix of brown & gray with black guard hairs). I actually* prefer rats that
aren't white (in terms of appearance or if I wanted a pet) but I've never had snakes that cared one bit. I've heard some BPs can be picky about this...most
likely it has to do with being fed live, getting bit by a rat & then associating the color of the rat that it got bit by as "undesirable" & something to fear. (Thank
you for not feeding live! Rats are intelligent animals, they can & do make excellent trainable pets.) So don't worry about the color of your feeder rats.
*I prefer more natural-looking rodents...white is not natural in wild rats as you realized, but all the coat variations in rats have been around for many years.
There are also Rex rats (curly coated) & Dumbo rats (ears set lower on the head like an elephant). I also breed domestic mice, again, in ALL colors including black, & have for decades. I keep very few white mice, the others are usually healthier & more vigorous.