Colored aleurone1 and Purple plant1 are both genes with long histories in maize research and are involved in the regulation of anthocyanin biosynthesis. The mutant version of purple plant1 does exactly what it sounds like. (In the proper genetic background) it has plants producing anthocyanin (a purple plant pigment) everywhere, resulting in purple plants. The mutant form of colored aleurone1 was identified from a mutant that changed the color of individual corn kernels. The two genes are also duplicates (homeologs) resulting from the maize whole genome duplication. More details, pictures of the mutant plants, a quick and interesting syntenic analysis and the mystery of the missing gene, in the full post.
Genetics: Studying the Source Code of Nature