Go out and look if the world around you is greyish and less saturated. If you go with open eyes you will see that the colours in CoD are quite spot on. Much more spot on than any other flight sim or flight game out there.

Only in memory your mind makes these colours seem less saturated but your brain is producing an illusion. That's why you actually believe that less saturated colours were more realistic while they are not.

And don't look at movies: most of them use colour filters and are therefore fake. If you want de saturated images tweak your screen settings and allow the rest of us play with realistic colours.