sexing red sexlinks and buff Orpingtons

[coolchick]

I have some red sexlinks and want to give some away but want to ensure that I keep the hens. they are 5 weeks old and have mostly red feathers. Is there anyway of confusing these with a male or am I safe to say they are all hens as long as they are mostly reddish? how about my Buff Orpintons they are 3 weeks, can I sex them yet. Thanks for your help