Males are usually bright pink in the combs by 10 weeks old. Pullets don't even begin to start to pink up until about 14 weeks old. By about 8 weeks old, red/gold-base color males already have 'rooster' red coming in on the shoulders/wing area. By about 14 to 16 weeks old; the long, thin, pointed male feathering is usually very visible. The hackle/neck feathers begin to take on a distinctly 'Fabio' type look. The saddleback feathers are long, very thin, and taper to a point.
X2 on junebuggena's post. Also in the case of Ameraucanas/Easter Eggers, the male typically have three rows of peas in their combs whereas females usually have only a single row of peas in their combs.