[My experience is precisely opposite… many if not most do have the right color. A very funny group of mix are the Camp Basenji rescued "lowriders"... mixes with basenji and some dwarf legged breed, not only same colors but most yodel and should more like basenjis than mine! If you go to BRAT, click on the mixes .. click each state, most look very basenji color.
My "job" with BRAT is to search the internet rescue sites daily looking for Basenjis and high mixes who may need help. One of the determining factors I always use is to see if the dog has hints of the Irish pattern (white on the feet, belly, chest, and tail tip). I don't think there's a Basenji mix without it. On the other hand, it seems many dogs with Irish white and large, prick ears are designated as "Basenji" by the shelters. Most aren't, but there are certainly some, and they always have a "look". I think that the dog that this thread was originally about is definitely part Basenji.