Each plant inherits 1 allele for flower color from each parent.

The 2 alleles segregate (separate) and end up in different gametes during meiosis.

Random fertilization yields predictable offspring ratios: 3:1 phenotypic ratio, 1:2:1 genotypic ratio.

These ratios can be modeled by a Punnett square: list all the possible female gametes along one side and all the possible male gametes along the other side, then combine the gametes to produce offspring.