Dilute (Di) is a dominant gene, so I doubt it could be hiding within a normally colored population. Di is also said to lighten shank color, which is probably why some buffs have the light shanks and toes. This must be some other recessive type of gene, if not ig (cream) then something similar which has not been discovered or named. The ig gene should lighten both males and females - do we know if this one does or not?
By the way, didn\'t John cross wheatens with silvers at one point? It might be very difficult to distinguish a silver wheaten female from a light, creamy wheaten female. Silver wheatens are described in the 1986 version of Bantam Standard.