Artists use contrast to separate shapes and areas from each other. Contrast is used with the background to bring certain objects out visually, or to draw attention to them. Adjusting the value of a space creates depth, with darker tones receding to the background and lighter tones appearing closer to the viewer.

This circle has neutral contrast.

The white circle looks like a ball against the black background.

The black circle looks like a hole on a white surface.

Contrast also helps define different color combinations. For example, there's a greater degree of contrast being between yellow and purple than red and purple. Yellow appears more visible against a purple background, while red doesn't stand out as much.