The Hulk was supposed to be grey. Creator Stan Lee initially wanted the Hulk to be grey, but due to ink problems, the Hulk turned out green. However, the misprint was explained in canon as the two Hulk personas (Grey vs. Green) fighting in Bruce Banner‘s subconscious.
100 Mind-Blowing Stan Facts
Stan Lee created the character for Iron Man as a challenge. Stan Lee had been playing around with the idea of a businessman superhero for a while and finally bit the bullet in 1963 when he came up with the concept for Iron Man. Marvel’s readers at the time were very much against war, so he thought it would be a unique challenge to create a character who fans would originally hate but come to love – and it worked!
The Incredible Hulk was initially supposed to be grey, but according to Stan Lee, an issue with the printer turned the Hulk green.