Why do iris change color?
If your iris are blooming a different color than originally purchased, it is because of letting your iris go to seed: the bloom stalk was not removed shortly after blooming. Bees do a wonderful job of pollinating different colors for the following year. The dominant color of iris is purple and will take over if the bloom stalk is not removed shortly after the bloom dries up. Chemical damage, overcrowding, and heat stress can be a factor in some color changes.