Originally, the Hulk was gray. I never read any of those old stories, so I'm not even sure what he was like. Because it was hard to color him, he became green. Later on, they decided to bring back Gray Hulk, but they gave him a meaner personality (as in, cruel, he was a jerk). He's either called Gray Hulk or Mr. Fixit (he was a mob boss in Las Vegas for a time). I think the Hulk with Banner's intelligence is just Smart Hulk.