I was sitting by someone on the bus a while back, and they had all their apps arranged by predominant icon color. Black on one screen, blue on another, green on a other, red, orange, etc... I can't imagine what sort of havock this led to in their life!
My apps are mostly arranged by install date. You just learn where everything is :) You stop using street signs after enough drives home.
That sounds like a pretty good way of organizing honestly. As long as you can remember where things are more-or-less within the individual screens, if you have a lot of apps installed and you have some that are only occasionally used, scrolling until you get to the color is a pretty easy way to narrow down where your target. I have some apps installed that I rarely use that I'd be more likely to remember what the icon looks like than the name of the app to search for it by text.
I heard that The Simpsons were made yellow because it stands out the most when quickly flipping through channels.