>>42737603Red wears a vest over a shirt in his classic design. This is corroborated by a promotional piece from 1995 and his model sheet for Let's Go.
Ash wore a similar looking short sleeved jacket over a shirt for his original outfit.
Red's vest in Masters is likely a nod to this design, updated to better resemble an actual vest and unambiguously drive that point home, much like how Brendan's redesign in ORAS made it clear he wears a knit cap.
Red's also not as serious as his art might lead you to believe; that's just his game face. He's implied to be a lot friendlier outside of battle.
