I have several modes of reading code, from scanning very fast to find a section (highlighting helps a lot), to reading at medium speed for obtaining overall gis

I have several modes of reading code, from scanning very fast to find a section (highlighting helps a lot), to reading at medium speed for obtaining overall gist (highlighting good?), to slowly reading for accuracy (highlighting not needed). It would be a pain to turn highlighting on/off since I switch modes rapidly and often. But I can image a mode where it changes highlighting based on scrolling speed. It would be easy fade the CSS colors to/from B/W on the fly.