In some types of wheat, color is caused by two sets of alleles. To produce a red color, both dominant alleles, R and B, are needd. White results from having both recessive alleles in the homozygous state, rrbb. Any other combination produces brown wheat grains. A strain with a genotype of Rrbb is crossed with a strain of wheat with a genotype of rrBb. What is the color of each parent strains?