Its okay for them to have the red phenotype at birth. It doesn't mean they will have red leakage as adults. When you are breeding the black/blue/splash colors there is always underlying copies of red, silver, or gold. Chances are they could be roosters, keep track of them. The brown color usually means they are carrying silver (I think). My Silver Laced Wyandottes always have some brown on them, as do the Australorps, and Ameraucana. Mama you can't cull day olds for anything except deformities (IMO). You have to feed a lot of babies to gather a nice starter flock. I know because I feed about 500 this past year!
Oh no, don't get me wrong. I am in no hurry to cull. I have plans to do nothing but grow out this year. But, I was told this will just mean read leakage in the blacks, which I do not want.