I just emerged (Gentoo user amarok 1.4 and enabled the moodbar feature. It looks nice, but actually I'd like to know how to interpret the actual colors. The exscalibar homepage is down atm, so I can't look there.
Does anyabody have a clue?

The moodbar is a visual representation of the differents "segments" of a music track.
It's supposedly made to help intra-track navigation (ie if you want to go to one prescise part of your music file).

The colors are meant to represent the feeling associated with the music. A darker color means no music, or a really quiet music, whereas a brighter/warmer color is associated with a lot of noise (i think).

I don't find that really accurate (but it's nice to look at even if it uses a lot of CPU during the computation of the moodbar).

Here is a link about the moodbar, with mathematical explanation and such: http://cratoo.de/amarok/ismir-crc.pdf