In one embodiment of the invention, photo-chromic applicators are disclosed. The photo-chromic applicator may include a liquid photo-chromic material such as a photo-chromic ink or paint. The photo-chromic material is applied to a surface of a toy, a page, or other object by a child user. The photo-chromic material may be activated in various ways with various light activating devices that can generate the activating light with appropriate wavelengths.