Japanese bantams come(to my memory) in black, white, gray, mottled, black-tailed white, brown, red, wheaten, black-tailed buff,cuckoo
On white Japanese bantams it is a disqualification to have legs of any color other that yellow.
Classes A, B and C are used to describe the size of a bird. A is the smallest and recomended as the Standard, with the weight/size increasing as you go from A to C.