[Eomer of the Rohirrim]

Now I am sorry if this question has been asked many times before but the search engine on this site treats me with contempt and I can't work with it.

In Unfinished Tales, Saruman (although I think he is referred to as 'The White Wizard') is said to have 'raven' hair. In every artist's impression of Saruman I have ever seen he has White hair.

This is surely nothing to do with age is it? Or is it something to do with his 'many colours' phase. Thoughts?