The Naphthyl Red moiety, conjugated to DNA, shows distinct chromism by hybridization with its complementary DNA. Single-stranded DNA involving the Naphthyl Red moiety exhibits an orange color and has lambda(max) at 466 nm at pH 7.0. The absorption maximum is shifted towards 545 nm by the presence of its complementary DNA, and the color of the solution changes from orange to magenta accordingly.