Method of producing color change in overlapping layers

摘要

The present invention relates to methods of producing color change in overlapping layers of material. The method comprises providing a first layer having a first activatable colorant and a second layer having a second activatable colorant. A first external stimulus is applied to activate the first activatable colorant and produce a first activated color region in the first layer. A second external stimulus is applied to activate second activatable colorant and produce a second activated color region in the second layer.