Don't color-coded bookshelves look so good? Maybe not the most practical form of organization though, so I doubt we will attempt it in the new library (still in boxes, alas), but I do love the way it looks!
(And yes, I know I need to get on Pinterest. Seriously. I will one of these days!)
And how about this one, the facing out book rails? So pretty.
And I suppose "white" is a kind of color-coding too:
Check out this video; it's an art installation called "There is Nothing Wrong in This Whole Wide World" from 2004 when this artist and a team of volunteers rearranged an entire San Francisco bookshop by color in one pizza-fueled night. Fun!