For example, place secondary DialogBoxes near their parent DialogBox so that when the secondary DialogBox appears, the mouse pointer is over the default PushButton , unless the user needs to see the contents of the original DialogBox. This stream of thought is disrupted when the user has to make unnecessary mouse movements, open and close DialogBoxes, or search for commands. Provide Natural Shades and Colors Minimize the contrast between screen objects in order to direct the user's attention. Appropriate use of contrast helps the user distinguish screen objects against the background of a window. If there are many objects with strong contrast or bright colors on the screen, the user will have difficulty knowing where to look first because all these objects compete equally for attention.
Differentiation also comes from the shape and size of the screen objects.
For example, in many parts of the world, stop signs are red octagons. You recognize the stop sign by both its shape and color.