welcome to the iris forum, Jolana. You are getting great responses so far. If the color change is significant I would think, as Mary Ann said, a bee pollinated a flower and the seeds scattered among the known rhizome and grew. Sometime on the older irises the children look similar to the parent plant and the new plants can be more hardy and actually smother out the parent plant. It is important to remove the seed pods in order to keep this from happening. Sometimes this is hard to do if you grow a lot. Good luck with sorting this out. It is a lovely iris.
