If its being grown in tissue culture, perhaps the pH of the culture media?

Usually it is caused by pH, but also genetics

It can also be a "sport" a portion of the plant that for some reason produces different coloured flowers or leaves. Many named cultivars come from these.

Thank you for these ideas. A

Plants frequently produce terpenes and alkaloids as part of a post stress tissue defense strategy. But I dont know if stress could cause flower color to change.