The main gene making them that color is called Columbian in english, Co in genetic notation. it is Very Dominant. What it does is mostly clear the body of the black pigments.. restricting it to the neck, wing tips and tail.
It has the strongest effect on wheaten, which is what your chicks are- light cream colored chicks. But many breeds have Co- RIR, light and buff brahmas, etc.. any mixes with these will strongly be colored like these as a result.
Try for birds with more black on body or more stripes as chicks to 'escape' Co..
But genetics is funny, Co is really important in some amazing patterns like lacing like on sebrights etc.
I don't know, but I think that I won't get wheaten ones. I don't like the colour and the other reason is that most of them have feathered feet and I don't like that.