This site talks about 2 flowers on one bush not specifically colour though.
www.jaycjayc.com/trophibiscus-rosasinensis-chinarose/ -

Thanks Drc726, interesting phenomenon of mutation of the flower, but the production of flowers of another color remains a mystery.
Now I have withdrawn my house plant, will bloom even in winter so we will see what color will prefer to show.

Do you think its just maturity of the plant?

I thought that maybe the arrival of the first cold has changed color, I do not know what will happen in the winter with the plants at the shelter, maybe spring will return ti its original color?

Forgive me, I'm using a translator, I do not write English ... but I think that the translator is not very capable

Its fine i can follow you perfectly.

Maybe the difference in light levels had made the earlier flowers fade?

I have a Hibiscus "moonraker" which was pure orange in first 5 flowers this was strange as it was supposed to also have yellow spots on the outer edge of each petal.But it did happen with flowers from no 6 on and still producing the flowers like the picyure on the label. The was the plant took a while to mature now its fine .maybe yours will change too .
another thought , maybe its reverting back to the colour of one of the parents as they usually cross polinate two flowers to breed a new colour.

Yes, but this doesn't happen on the original plant, only in the offspring.