Putting a stop to a sea of internet rumors today, Marvel spokesguy Avi Arad said the new Hulk will not be grey.  EmpireOnline had a quick chat with Arad, where he denied the rumor completely.

“It was a joke!  Here’s what it was. There were 30 people around a table, and they said ‘is there going to be a grey Hulk?’ And I was thinking about it and I said, ‘who knows?’ It was one of those moments.
I had just got back from Japan and I was trying to talk about Spider-Man and this guy was pushing me on The Hulk so I thought I’ll be coy. I don’t know what colour it is, and all of a sudden it’s headline news.”

Arad also confirmed that the Hulk will be taking on The Abomination this time out.  More interestingly, he mentioned the recast of Betty Ross and that an announcement should be made within the next few days.  We'll have to see if that Jessica Biel rumor has some meat to it.