sorry - i have a third response, and i'm posting it here because i've seen this in a bunch of different articles and it needs to be addressed. i previously stated that the stuff about the lighting was right, and it is, but i meant the stuff about natural versus artificial light. that's important. maybe less important than screen contrast, but important.

however, this idea of "colour constancy" is really utter garbage. you present the rubik's cube, with the brown in two different spots and a shadow on one, and then suggest that your brain "creates" the orange to "compensate" for the shadow. in fact, it's the shadow that creates the orange by placing a filter over the cube, and your brain sees it as orange because it is orange through the shadow (like the red and green are a little darker). you want to talk about additive mixing here. and you can see something similar by attending a concert with a light show.