Ya that works on a lot of breeds/varieties. Pretty much any of the duckwing, partridge or wheaton.My wellie cockerels get black feathers on their chests at about 4-5 weeks while the girls stay red/salmon. It's always a little disheartening to walk out there and see black speckles starting on a few of their breasts...
I love it because although it can be disheartening its bomb proof sexing.