Good script, although from the name I expected more, well, colour. The script adds different greyscales to the backgrounds of tweets based on age. That's easy enough to change though, and after some experimentation I found these colours look nice, and when used in order give a nice fade from recent=warm to old=cool colours.

#ffbbbb
#ffffbb
#bbffbb
#bbffff
#ccccff

Where this would be great for use though is on Twitter's homepage, not just on friend's profiles. I tried to make that work but I couldn't.