Remember that color, shape, value, is relative to what it's surrounded by. In addition our brain will shift our visual perception of value to level adjust our vision/perception.
To prove the theory stare at the yellow box or the red triangle intensely for 30-60 seconds then stare at the blank white space after it. You will notice that the after image is the exact complimentary color of the shape you had been staring at.
The center green block here appears to shift value but it's actually a solid colored block.
Here the character appears to have warmer skin and cooler hair, but the image is really monochromatic in HUE. The hair is the same HUE as the skin but because it's desaturated it appears cooler the skin which is more more saturated.
