Final answer:
The genotype of the purple-flowered parent is BB and the parents are heterozygous for flower color, Bb.
Step-by-step explanation:
The genotype of the purple-flowered parent is BB. The Punnett square shows a cross between two heterozygotes, Bb. The offspring will show the dominant purple coloration in a 3:1 ratio, with about 75% of the offspring being purple. The parents are heterozygous for flower color, Bb.