Colors of objects closer to the observer show a high contrast, whereas objects farther away appear lighter and with much less contrast.
When used with shaded relief, aerial perspective serves to differentiate between high mountain summits and lower, more distant lowlands. When aerial perspective is applied, contrast gradually sharpens towards the highest peaks and softens towards the lowlands. The highest amounts of contrast depict the highest mountain peaks.
Imhof's map image "Walensee" uses aerial perspective in an ideal way.