Dendrobium nobile changing colors?

[Yen]

Hi everybody!
I started researching and experimenting with den nobile and I'm hoping if someone can answer me this question...

So I've been googling/youtubing den spring dream apollon and some other white den nobile... I noticed that some people's spring dream apollons would have a tinge of pink to the petals/sepals of their orchids in one year but would be completely white another year... why is that? Does it have to do with genetics or simply external factors like temp/humidity/watering/etc...?

Thanks!!