I always thought 5-6 weeks was the perfect time to pick out the cockerels on most breeds,5 weeks is very early to tell but if it's the same breed as the others but distinctly different there is a pretty good chance yes.
If it's a different breed then don't give up all hope but be prepared for it. I've asked sex 3 times here at that age and 3 times everyone got it wrong ;-)
that's when their comb color pops out and wattles start growing and coloring too.