Gamma energy and adrenaline combine to turn Hulk into a green monster.
There is no definitive answer but the most plausible one is that it's a neutral...
The Incredible Hulk often uses the saying, "Hulk Smash and Bash" before turning...
Real Name of the Incredible Hulk is: Robert Bruce Banner. !
The only answer I can give you here is it is "TV magic".
It doesn't say why the Hulk turnd green when he's angry. .