I didn't read it on a book, but on a forum. I suppose it was on this one, but maybe on a French one. I've visited a lot of OTMAA and NAOTMAA sites and blogs in the last five years.
I don't know why the whole matter is so terribly important. The Emprees could have said it or not. My own granny - who is NOT and Empress always said that I should be prettier with lighter hair, cause my face is a little pale and a blondest hair could have enlightened it (my hair is dark blonde, as Olga's one). And I'm sure that my granny didn't want to be mean when she said it...
RealAnastasia.