If it's an actual Leghorn, it might be a pullet - I agree better pictures are needed. Leghorn roosters develop their secondary characteristics, including feathering, VERY early, and Leghorn hens have big combs and wattles. That bird has awfully henny feathering if it's actually 4 months old. If it's four-close-to-five, since the OP doesn't know exactly how old it is, it could be red because it's coming into lay. If it's been red like that since it arrived, or if it might be younger than four months, then I'd agree cockerel.
In-focus pics of feathering and color will help us the most.