The genetics of snapdragons?

It would seem that two different gene products are required to convert a colorless compound into the purple pigment. The California plant and the Dutch plant have mutations in different genes. Genetically, the first plant might be AAbb and the second one aaBB. WHen you cross those, the F1 would all be AaBb, and the F2 would be 9 A_B_:3 A_bb:3 aaB_:1 aabb. Only the A_B_ plants would be purple, so you would see a 9:7 purple:white ratio in the F2.