1. Anyone can do it. Even the decor-challenged.
2. It costs nothing if you already have books.
3. It reduces visual clutter.
4. Rainbows are pretty.
5. Cortney Novogratz does it on the teevee and that makes it right.
6. Gives people the (sometimes false) impression that they’re dealing with a highly organized person.
7. Bunching books by color makes each color POP.
8. Beats the heck out of the Dewey Decimal System Home Edition.
9. Rainbow’d books are a subliminal way to promote marriage equality.
10. Not colorizing your books is just pure spine color anarchy.