That's nice too. The only thing I'd suggest is having the px as negatives, but that's because I actually didn't think it was working for a bit since I tend to read the left side and totally missed the highlights on the right.
Edit - I just realized that while this point is true on feeds, once you get into the comments putting those colors on the left side would mess up the coloring that shows a tree of comments since that's also on that side. So the fed colors really need to go on the other three sides to be compatible.
A preference setting for this (in the future) could have a huge number of styles to pick from. Some people may even prefer the original simple background color.