We have yet to see what other colors the Hulk will take on next. Heck, I was curious about the pink hulk from the thumbnail with the thought itself being clickbait. And you caught me!
The Grey Hulk and Joe Fixit are 2 different personality. Though both Kluh and Titan have black skin, only Kluh is considered the Hulks of Hulk. Unless that changed? I also don't think Titan is a true personality, given he was putt in Bruce's head by D'Spayre under orders from the Leader who was changed by The Green Door. The Purple Hulk isn't Shanzar, but Osborne. Shanzar who possessed the Hulk, took on a White with Black shading and fought Strange and Namor. So Shanzar Hulk could be count as a 3rd White Hulk. But there was a time when Hulk became Nul and was a shade of Purple. Xemnu, I never considered him a Hulk. Yes his hulking, but his a giant robot alien that once called himself Xemnu the Living Living Hulk. But I think he only called himself that in his 2 solo comic runs, after Hulk was made he went by Xemnu the Living Titan. But if we're counting non could characters then Glop who's original name was Hulk before they changed it do to Brace/Hulk being created is Orange. So that would be 2 Orange Hulks in the main 616 and 1 alternate. There is also a guy called Viking Hulk and he has Black skin, so that would be 3 in the 616.
