RIR chicks... Can I tell them apart by head color at 5-6 weeks?

[zowieyellowflame]

Hi,
I have 6 RIR chicks and I don't remember how they looked as a day old but right now, at 5 or 6 weeks, 5 of them have dark heads while one is a light colored head. (distinctly different coloring on the head only) Wonder if this could indicate sex at all or did they just mature at different rates?
Thanks

 

[pattypenny]

I don't think the color of the head denotes sex but soon the combs on any roosters should start growing and be more noticeable.