I have had a few strange colours this year. My Rosa filipes seedling that normally has a pink bud, but opens to white,has all pink flowers at the top of the hawthorn where it gets more sunshine. The rest of the flowers are white.
I have a dahlia,that for 2 years has been peach and coral, but this year is opening a much deeper colour.
certainly some sweet peas that I have are a much deeper colour than on the packet. I have put it down to the weather. I cant see what else would be different. The dahlias are in a different position, but the rose is neither pruned nor fed.