Ehh, I wouldn't call it racism, since black/brown/white/etc. wolves aren't a race. Wolves as a whole are a species/race, but the colors alone don't indicate a certain ethnicity or region of origin like it does with humans (in FH, anyway).
Do some people just kind of prefer a certain color palette, though? Well, yeah. Black is a classic color that goes with almost any other, the same way some people like dressing in all black with different colored accents, or prefer a black and white pair of shoes over a brown one.
Certain color palettes tend to be more appealing to the masses than others, put simply.