I'm sure thats what it is...he is just maturing and its the male in him!...The first time I ever saw this in my young BO roosters that I hatched from Hinkjc, I asked her what it could be...she told me the Rooster get red streaks in the legs...its blood flow I believe...You can always PM her and she can tell you more.....
It's fine. Just seeing the blood going though the legs easily since he doesn't have yellow pigmentation to cover it up like other breeds. Like blushing, just on the legs... all the time!