Variety is the design concept that breaks the monotony of others like proportion and harmony by introducing elements that create interest. When applying these concept you apply into a design colors, shapes and textures that catch your attention.
Contrast is used to enhance or decrease the value of a design element like lines and shapes, or the value of other concepts like proportion. By using contrast colors may look lighter of darker, shapes seem smaller of bigger and placer look farther or closer.
Use These two concepts to make simple spaces more interesting, to increase the visibility of a graphic design, or to create focal points out similar objects.
Have a lovely day and hope to be able to see you more often this week!