A Princess who wears white and is innocent and pure is turned into a dragon. I seem to remember that she has to fight princes and knights who come to rescue her, not knowing that the dragon is the princess. I think she has to kill a few of them to defend herself. When she is finally turned back into a princess, she wears gray, which symbolizes that her soul is stained. I think the book was published before 1994, although I might say 1996 to be safe.

I have been thinking about this book for the last twenty years! Thank you for your help.