The flowers on the motherplant and the keiki are not the same!

[Saiva]

My father has had a Phalaenopsis hybride for 7 years now. It has produced 3 keikis during that time and no. 1 and no. 3 have the same type of flowers as the motherplant.

But keiki no. 2 got different flowers! It's blooming right now for the second time and the flowers are still different.

This is the motherplant:


This is keiki no. 2:




I thought that the keiki ALWAYS got the same flowers as the mother plant but not in this case...

Is it common that they get different colours?

Any ideas?