Photochromic dyes are disclosed. A photochromic dye can include a first photo-reactive group and a second photo- reactive group. A first photochromic reaction can be induced in the first photo-reactive group of the photochromic dye by radiation having a first wavelength, and a second photochromic reaction can be induced in the second photo- reactive group of the photochromic dye by radiation having a second wavelength. The second wavelength may be greater than the first wavelength.