The etymology of the color names in Quenya and Sindarin:
White: from the root *glân, (S and Q) originally meaning pure. However, I don't believe the word pure implies Saruman (who's original name Curunir translates as cunning) but to the White Council he preceded. The White Council was formed to challenge Dol Guldur, the lair (dol) of the Necromancer (guldur), literally "perverted or evil knowledge". It therefore stands to reason that the name White Council was chosen not for the color, but the implied purity of knowledge protected by that council.
Grey: *mith(S), Gandalf was called Mithrandir, Grey Pilgrim, by the Eldar.
Blue: The Blue Wizards Pallando and Alatar are called the Ithryn Luin because it is said they arrived in Middle-earth by boat dressed in sea-blue (luin). However, luin stems from lhun, which also means boat.
Brown: no translation for Radagast is provided by Tolkien. However, a possible root for the name may be the Old English rudugást, meaning brown spirit.
via Gulhir the Grey
Tags Saruman the White Gandalf Pallando Alatar Radagast the Brown The Necromancer The White Council The Eldar Dol Guldur Middle-Earth Quenya Sindarin