Do, Cna lilies change colour?
Depends what kind of colour change they mean, I would think. The colours are determined in part by the plant's cell chemistry, which responds to the environment. So flowers are often affected by position, in sun or shade, or by temperature, and also by the age of the flower itself.
There are also external influences, such as virus or chemical attack that may cause genetic mutation, such as Rembrandt tulips, and there is reversion too. I used to have many blue bluebells, but over the years they have become predominantly white.
Of course many flowers may differ also drastically from the catalogue pictures, if they were photoshopped