For it's age, I'd watch it as it's looking more like a rooster. Could you get a whole side shot of it, as it looks like the color gets darker in the back.
I wouldn't go sexing chicks by their tail lengths at that early of an age. I know a person who swears by this method, "she can sex any bird at two weeks of age by the tail growth". Then she turns around to ask what sex we think they are. It has turned out that most the ones that she picked out...