It gets cold while running at sub-warp speeds! Just ask the Flash...he knows! Why else would you bother to wear a full body suit like that? It certainly isn't for breathe-ability! It is more like a giant wind breaker. That red color of his also helps to absorb the infrared light spectrum, warming him just a few degrees. Of course the Flash got to kick all of that to the curb for 24 hours when he was deputized a Blue Lantern by Saint Walker himself! Hey, they had a lot of zombies to deal with....super charged zombies. Super speed might not have been enough, but the blue light of Hope makes a perfect supplement for the Scarlet Speedster. I'm sure the Flash was jealous of all of those neat things Hal Jordan could do, so now it is the Flash's turn. We know you love the Flash, we know you love the Blackest Night, so why don't you just combine your love of both of those things into some weird human centipede like 90% cotton 10% polyester amalgamation....the Blue Lantern Flash Hoodie! Ok, so it isn't that weird. I just wanted to reference that twisted movie!