After a bit of searching, the best I can tell is that "Light Brahmas" are supposed to have a Colombian feather pattern. It seems that the all-white Brahma color pattern is not recognized by the APA. However, that said, it also seems that shows may have an "any other color" category where I guess you could put them. Please note there's a lot of supposition going on here, and this is just what I found with a few minutes searching.