Posted: 03/05/2012 at 14:11
Yes, flowers can change colour as they develop, and many, many do. Take a look at my blog from last autumn about Tulip 'Antoinette'. This tulip starts as a pale yellow colour, but gradually becomes more pink as it develops and faded.
You can see the same thing happening with many roses too.
This is a very different thing from a new plant growing with a different coloured flower from its parent, or perhaps one stem on a plant carrying flowers with a different colour from teh rest of that plant.