Rated 4 out of 5 stars

First of all this is very useful addon. Dynamic highlight is nice. But there are some bugs. Sometimes layout of site are broken because of injected span elements (for example try to google something on digg.com). Perhaps css rule "span.ColorResultsClass {display:inline}" will help.
Also it will be good to have an option to highlight a fragment of text directly from the google result with another color and scroll to this fragment automatically.
Excellent idea, five stars. But not perfect implementation. So four stars for now.