As you can probably tell, images such as these are made to illustrate the limitations (or amazing capabilities, depending on your.. perception) of the visual system. The chess pieces, and the horizontal bar are of the same/uniform colour, but their surroundings cause us to interpret the true colours in different ways.

But what about more everyday examples in media? Truthfully, selecting colours in the creation of artwork is all about this. When I first started off making artworks as a child, I would always be mildly confused as to the end result of my works - I was always choosing the "true" colours as I had imagined them in my mind, so why was it that the final product seemed so garish, unbalanced, and generally unrepresentative of my intended portrayal? Probably it didn't help that the color pencils and crayons I started out with were rather limited to begin with, and didn't mix very well in any case, but the idea is that choosing colours separately for every object in your artwork is going to make the end product look like it was stitched together from different worlds of coloring - they were colored that way, after all. To achieve the harmonious look like in so many famous paintings, artists would often have to do a layer of underpainting to better define the values of the colours first, and then concern themselves more with application of colour. The modern digital version of this is first completing an artwork in greyscale, and then using another layer (usually set to modify or overlay) to paint on the colours.