The Jargon File (version 4.4.7, 29 Dec 2003):

blue goo
 n.

    Term for ?police? nanobots intended to prevent gray goo, denature
    hazardous waste, destroy pollution, put ozone back into the stratosphere,
    prevent halitosis, and promote truth, justice, and the American way, etc.
    The term ?Blue Goo? can be found in Dr. Seuss's Fox In Socks to refer to a
    substance much like bubblegum. ?Would you like to chew blue goo, sir??. See
    nanotechnology.