dimorphic ??? old english game bantam ???

[sussex x]

hi , 2 chick hatched a couple of day ago , 1 of the chicks has a different colour .the first is darker with a tint of brown a the back , and redish' on the small wing feathers . the other is a lot lighter with no colour ( visible to my eye ) on its wing feathers . the birds are from Wheaton parents , are they dimorphic ???
regards

 

[foxy]

Yes they are, I am not sure how distinctive they will be as chicks though, the paler chick I suspect will be the female.