Over two years later, via my man Kottke, I finally get an answer to my question about flooded fields in San Francisco bay that I saw from an airplane.
Turns out they're salt evaporation ponds, and the colors are caused by different forms of algae that grow in different salinity conditions--the red ponds are the saltiest.
I also just got a great song title/travel idea from that article: Useless Loop, Western Australia.
