Males exhibit more colorful plumage than females in many bird species. Phylogenetic reconstructions indicate that transitions from dichromatism to monochromatism are not uncommon and that monochromatism can result from the evolution of brighter plumage in females. To better understand the time scale over which such changes in dichromatism can evolve, we used a reflectance spectrophotometer to quantify feather coloration in the Atlantic Canary (Serinus canaria), a species that is sexually dichromatic in the wild but that has been under strong artificial selection for color in both sexes for several centuries. We measured the plumage coloration of males and females in the wild progener population of canaries, in captive canaries bred for bright yellow or red plumage coloration, and in Black-hooded Red Siskins (Carduelis cucullata), which were hybridized with yellow canaries to produce red canaries. We show that domestic canaries evolved from dichromatism to monochromatism under strong selection for increased female coloration in <500 years and that red canaries, the hybrid lineage resulting from canary-siskin crosses, evolved from dichromatic to monochromatic in <75 years. These observations show that bright monochromatic plumage can rapidly evolve from a dichromatic ancestral state.