"Thus we meet again, though all the hosts of Mordor lay between us." Aragorn, Battle of the Pelennor Fields.
There are some mysteries that should stay mysteries. Saruman's robing habits is one of those things. Unfortunately, we at EXPLANATIONS are too stupid to make the distinction. And are also too stupid to own Lord of the Rings or any paraphernalia used as product placement within the bounds of this article.
EXPLANATIONS Episode 2: Why Saruman Only Wore White
Saruman glanced into his Palantír (which wasn't there because it compromised the rules of the Wizard Council and he could have his robes dyed khaki). "Oh, Gandalf's coming," he announced. "Gríma."
Wormtongue failed to appear.
"Gríma!"
A black-haired, greasy-looking man (and we're not talking pop stars) refused to pop out of nothingness.
"GRÍMA!"
Wormtongue still didn't appear.
Saruman threw a wizardly tantrum, screaming 'Wormtongue' repeatedly. An Uruk-hai appeared from behind him.
"Lord Saruman," it said harshly but respectfully, "You sent him off to enslave the mind of Théoden King to your evil will."
"Ah yes, that's right!" the White Wizard exclaimed. "So you'll have to wash my robes. Be very careful about how you go about it, if the water is too cold then the colour-change chaunt shall be destroyed."
The Uruk-hai bowed and took the dirty robes basket, diverting his eyes from the ...disturbing... sight of his leader in short-shorts and a singlet top. Saruman watched him leave.
"Ah yes, Clarissa[1]," he said evilly, "You shall wash my robes!"
The White Wizard threw back his head and laughed evilly, stopping only when his hair lost its sleek, shiny Sindarin-wannabe look. He immediately set about giving himself an evil-ageless-wizard makeover, complete with UV- activated multi-coloured nail hardener.
Time Lapse
Clarissa stood in the Orthanc laundry. He didn't usually do laundry; in fact he was more of a seamstressing type of Uruk. He glanced at the turndials. Trust Lurtz to order an Elvish washing-machine. Bloody military types, created without brains so they could fit into their tin hats.
With one hand, he dropped the pile of slightly dirty white robes and used the other to pour half a bottle of bleach ('White Wizard') in. The White Wizard disliked being The Slightly Off-White Wizard, as several Uruks had found when they forgot to remove a stain. The janitorcs were still trying to scrape them off the ceiling.
Spinning one turndial to what he assumed to be 'White Wizard Wash', Clarissa tried to look like he was just standing around in the laundry looking for some crisped Manflesh and beer.
"You know that they run for an hour?" a laundromorc asked him.
"...oh," Clarissa replied intelligently. He left the laundry in search of some socks to darn and Men to crush mercilessly and eat raw.
Yet Another Time Lapse
Gandalf galloped up impressively on his horse. Saruman walked down the stairs and greeted him.
"Alf. My old... FRIEND."
"Sarry. It's nice to see you. I brought our holiday photos."
"Ah. Come upstairs and we'll look at it over a pipe, in my throne room of ultimate ev- I mean, my nice cosy living room, in front of the TV."
"Sounds good," Gandalf replied. He made his way up the great stairs.
Saruman followed him inside. "Holiday photos. You shall regret this slip, old friend."
Time Lapse Number Three
"Sarry! You have turned to Sauron! What happened to the wisdom of Saruman the White?!"
"I am not Saruman the White!" Saruman shouted. "I am Saruman of Many Colours!" He flung out his arms and waited for the robe to flash. It refused. He glanced at the ceiling, and then repeated the gesture. The robe remained a pristine white.
"Well..." Saruman coughed. "I can prove that I'm right and you're wrong."
"How?"
"Go check out my Palantír. It has seventeen channels as well as a direct link to the Dark Lord's chatroom."
"You have betrayed us!" Gandalf shouted, waiting for his staff to blast the Head of the Wizarding Council backwards. It appeared not to work either.
Silence reigned for several minutes, only broken by embarrassed rheumatic coughs.
"Well, I can still blast you through the tower roof," Saruman finally decided, and did so.
Very soon after that, the Orthanc security tapes were severely altered to show an exciting fight between two wizards, rather than two old men discussing holiday photos. Saruman decided not to go 'Many-Coloured', and Gandalf found a bottle of White Wizard [2] after his "death" when he fought the Balrog.
And they were still trying to scrape Clarissa off the foyer walls when the Ents tore through them.
[1] Uruks don't seem to understand, do they?
[2] Maiatifically Proven! No More Greys! Guaranteed!