You can make the colors as vibrant as you want in Gears, and as for AC, they are using different filters for different places.
for example, in city 1 you will see the blue filter, city 2 is yellow filter, etc..., don't know how much filters overall though.
i don't mind them using filters, but in MGS4, all we saw so far is one ugly yellow filter, it's like Kojima is convinced that the middle east is all yellow or something.