" A young, fourteen year old boy about 5'5 that wears a dark green shirt, leather jeans, a red scarf, and a large blue beanie..."
If you really want to devote a couple sentences to describing a character it could look similar to this:
Something like that COULD work, but I think what the others said it the best way to write. You shouldn't really focus too much on what he looks like. You want to readers mind to flourish with their own creative ideas while reading instead of being directed too much.