This image shows a dialog that is clearly in the foreground. It draws the user's attention with the darkening of the page behind it. 

Example 1

This image shows how color can make fields pop into the foreground.

Example 2

Figure-ground can be used to show the user what they should be paying attention to. This can be done with dialogs, navigation panels, and use of color. 

University of Michigan - Ann Arbor

The figure-ground principle states that "people instinctively perceive objects as either being in the foreground or the background." The user knows that the foreground is more important than the background.

The Law of Figure-Ground

"What are Gestalt Principles?" Interaction Design. https://www.interaction-design.org/literature/topics/gestalt-principles

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