First, one must understand the difference between genotypes and phenotypes. Genotypes is the letters associated with the traits present and phenotypes are the physical features shown.
In order to have an organism display a recessive trait, you need BOTH alleles to be lowercase. If the problem specifically mentions codominance, then there is a mix. However, because it doesn't mention that you can assume blending does not occur.
The parents would have to be Rr (Heterozygous Dominant) and rr (homozygous recessive) because the Rr genotype allows a parent to be a red flower but also have offspring that have white flowers. A homozygous dominant parent (RR) would not be able to have offspring that show a recessive trait.
