Geez... I looked all over for pictures in order to do my Kazuhiko costume and I don't think I ever once found a color image of Ballus. And I even looked in several CLAMP artbooks as well... so, yeah, I'd have to agree... I don't think that a color picture was ever done of him.
If you're making a Ballus costume I'd suggest just using whatever colors you think work.
*giggles* It'd be cool to see a Ballus. ^_^ *must finish his Kazuhiko sword*
Jeremy "Z-san" Forbes
"You have much YAOI-esque-ness here...!"