Seems to be a possible mix due to muffs, straight comb, yellow legs as others mentioned.
His coloring reminds me of a blue splash cockerel we had. Although we got rid of the 3 males of that breed (we bought straight run), we got one male of each: black, blue, splash, and the splash had a similar light and mottled appearance. I’m not familiar enough with blue genetics to say he is a splash, just has some similarities to the one splash male we had.