Shouldnt he be ESB colors instead?
I don't think the game designers, or the ILM people notices or are really concerned regarding the differences of the ESB or ROJ armor. To them, Boba Fett looks the same irregardless of whether he's wearing ESB or ROJ armor. (It's whatever looks good on Boba Fett in film at the moment.) While the fans are very detail oriented, in regards to the differences between the ESB and ROJ armor, this may not be the case with the ILM employees or Lucasfilm's wardrobe department employees. One of the reasons that the ROJ armor was different from the ESB armor, was because the costume designers had to make some adjustments in order to make it fit better for the actor. (I remember the OT Boba Fett actor, Jeremy Bulloch had said something in the past that the gauntlets from the first ESB armor were pinching him, and the jetpack's straps were rubbing on his shoulders when they were filming the "Carbon Freezing Chamber" scene.) The ESB armor was still experimental, and the costume designers were trying to see what would work, and wouldn't work on the actor.
This was also evident during the 1997-1998 "Special Edition" versions. In the "Special Edition" version of ANH, the Imperial Sandtroopers patrolling the Tatooine desert were wearing the ROJ armor, instead of the ANH armor in the newly inserted scenes. (Their helmets were also blatantly ROJ.) When the wardrobe department fitted the armor and suit on the Boba Fett actors during the "Special Edition" scenes for ANH & ROJ, I don't think they cared whether it was going to be ESB or ROJ armor. It was whatever looked good on film at the moment. Even Darth Vader was walking around in a ROJ helmet & armor during the newly inserted scenes for the ESB "Special Edition". Boba Fett's body type, mannerisms & posture were also noticeably different from the OT Jeremy Bulloch's & John Fass Morton's version in the newly inserted "Special Edition" scenes. The "Special Edition" Boba Fett were played by Mark Austin, Nelson Hall, & Don Bies. (All 3 of them were ILM employees, and weren't actors, so it was obvious that the casting department grabbed whoever was available for the part at the moment.)
It certainly would be nice if Lucasfilm would hire some of the Dented Helmet fans in the future as technical advisors. They certainly would pay more attention regarding the subtle differences between Boba Fett's ROJ and the ESB armor.