Flower color in a particular plant species is determined by one gene locus. The allele at the locus can code for either red flowers or blue flowers. When two such plants are crossed, however, some of

Flower color in a particular plant species is determined by one gene locus. The allele at the locus can code for either red flowers or blue flowers. When two such plants are crossed, however, some of the offspring produce purple flowers. What is the genotype of the plants with purple flowers?