Question for All You Horticulturalists Out There

About 5 years ago, we planted 4 Oriental Poppies. Each year they have produced  magnificent flowers, more and more each year. This year we have had 24 blooms, all nice and orange, as they should be.

 The flowers are stunning!

 However, this year we have had one white poppy, now gone and today out pops this pink one. The originals were all single root plants, producing orange flowers.
How did the white and pink variations sneak in?

Now, I am not complaining, just curious. There are no other poppies in this end of Whitecourt, and no others that I have seen any where in Town.

I guess I will have to go and contemplate  my navel until someone comes up with an answer.