This is High Dynamic Range lightning, or HDR for short. From my first day playing i could see that the game was absolutely saturated with the stuff, though i guess not everyone likes it - in certain scenes I think it's a fantastic effect and i'd rather always have it on.

What does puzzle me is that they do not have an toggle for it in the config, every other game I can think of has this as an optional effect, for the simple reason that it's quite a relatively big GPU hog and the game would run much better on low end systems with this turned off.