Another genetics problem....?

You cross true-breeding red-flowered plants with true-breeding, white-flowered plants, and the F1 are all red-flowered plants. The F2, however occur in the ration of 9 red: 6 pale purple: 1 white. How many genes are involved in the inheritance of this color character? explain why the F1 are all red and how the 9:6:1 ration phenotypes in the F2 occurred.