This generation of games as one unique quality to it: a brownish tint. Naughty Dog games have a lot of lush color to them, so to make Uncharted 2: Among Thieves a "true" next-generation title, you need to offer games the option to make the game look a little drab. Much like Uncharted: Drake's Fortune, Uncharted 2 features a 'Next-Gen Filter', which you can purchase with the in-game money. Unlike Drake's Fortune filter, this time around it's much more accurate and comical.
Screens added in article for comparison.