Wow look at that... looks white/tan to me. But yeah, they should have went with black since the rest/majority of the movie he was wearing a black belt.
It's not unlikely that they had several belts in wardrobe, some slightly different from others. That often happens in movies that an article of clothing will change slightly from scene to scene. Besides, it may be the difference between the belt he wore with the black shirt, and the one he wore with the gray shirt. Sideshow just got them backwards from what I see throughout the pics posted in this thread.