In The Fellowship of the Ring, during the Council of Elrond at Rivendell;
Gandalf relates the tale of the fight which he had with Saruman in Isengard.
‘For I am Saruman the Wise, Saruman Ring-maker, Saruman of Many Colours!’
I looked then and saw that his robes, which had seemed white, were not so, but were woven of all colours, and if he moved they shimmered and changed hue so that the eye was bewildered.
‘I liked white better,’ I said.
‘White!’ he sneered. ‘It serves as a beginning. White cloth may be dyed. The white page can be overwritten; and the white light can be broken.’
‘In which case it is no longer white,’ said I. ‘And he that breaks a thing to find out what it is has left the path of wisdom.’ – Gandalf