Color Effects?

They applied a revolutionary technique to the film called "The Crush". What they basically did was turned up the contrast of the film to the 11.

Basically what they did was they shot the normal image on film and lit it beautifully. Then in post, they turned up the highlights to the extreme and the shadows to the extreme. So that there are extremely bright areas and extremely dark areas co-existing on the screen, which looks very unnatural and hyper-real. The colors suddenly bloom and start popping off the screen - the crimson of the blood and capes, the brown tan of the skin, the golden glow of the Spartan weapons and shields and helmets. But it closely resembles how comic books look, they also have extreme contrast, so that both very dark areas and very light areas exist in panels.

So that's how the look was achieved, so that it looked extremely high-contrast and very hyper-real, like a dream almost. Over that they also applied some color tones over the image, like golden over everything else and blue over the night scene, to add some more color.