If red starts coming in on the wing that's a huge marker for a boy. Bigger redder three row pea combs before a certain age also generally means boy. However, there are usually a few 'stealth roosters' in all of my hatches that don't have red combs, red on the wing, etc - and are STILL boys, just late bloomers. And you can certainly have a completely solid color EE or AM boy - just the red on the wing tells you for SURE that it's a boy.
