An embodiment is a display unit. The display unit includes a substrate layer, a layer of colored fluid on the substrate layer, and a transparent actuator element on the layer of the colored fluid. The layer of colored fluid has a thickness and a color. The transparent actuator element modulates the thickness of the colored fluid upon activated by a force such that the colored fluid is changed from a first state to a second state or vice versa. The modulated thickness provides a variable optical density of the colored fluid.