The modern day Red Hulk is actually long time Hulk nemesis General Thadeus 'Thunderbolt' Ross, who offered himself to a procedure that would replicate the accident that created the Hulk, however unlike Banner's Hulk, He does not increase strength with rage, and can absorb energy and turn it to strength. Bruce Banner's Hulk was able to transform into a red incarnate of his Hulk through such a level of rage, and some mystic enhancement. They called it Devil Hulk i think. Its been ages since I read that far back, so don't quote me on that last bit :)Hulk isn't Red, Red Hulk is Thaddeus Ross that is Red She-Hulk's father. And now he's a Avenger.