What is it with people pissing and moaning about color...? It was the same thing with Diablo 3, and whatever flaws with that game (and there's plenty!), there being colors in the graphics is NOT one of them.
The PS4 KZ demo uses color really skillfully IMO, here you're being betrayed from within, in your own home, by the enemy. The bright sun and rich colors of "your" side of the city accentuates that. As you can see at the end of the demo, the opposite side of the world looks a LOT more oppressive, yet people get all hung up on what the "side of freedom" looks like.
It's just ridiculous, really. People complaining about this really have no sense at all.
It's similar to Diablo 3, but it's not the same crybaby nonsense. If you played Killzone 1 when it first came out, you would understand.
No one has complained, for example, Killzone is not violent enough. Diablo 3's colour palette changed much less from Diablo 2 than Killzone Shadowfall has from KZ1 and KZ2. It's a much bigger difference. And people were calling that a cartoon. No one has said Killzone looks like a Saturday morning cartoon either, only that the change is noticed.
The reason for the colour palette in Killzone 1 was part of the different direction the directors wanted from other popular FPS. It was inspired by real wars, like WW1, except in space. The first level drops you in a trench in front of a minefield on Vekta, that should say something about the feelings they wanted to evoke. And no one can deny the parallel between the Nazi soldier gear from WW2 and the appearance of the Helghast.
The complaints aren't really about colour. It's a much bigger change than you make it out to be. Fans who were there from the beginning would understand. One of the things they used to talk about in the original Killzone is that they would never use laser weapons or anything that would seem unrealistic for a post-modern WW2 in space... enter Killzone 2 and 3 and there is a huge change, there are laser weapons.
It's not only the colour people would be worried about. Killzone 2 and Killzone 3 utterly destroyed the story telling in the series. Especially Killzone 3. GG has a problem it seems of taking too much inspiration from other games, especially with how 'dudebro' Killzone 3 is.
It's about series direction. Some people loved the WW2 in space, fighting nazi's direction. Like me. I'm sure it will be a great game in the end, but the sequel most fans wanted if they were there from the beginning was a true sequel to Killzone 1 and 2.