A generic term for contact adhesives, all of which may not actually be green in color. The classic industry standard is 3M's 30NF. Used primarily in laminating countertops and table tops. It is unique in that it is applied to both surfaces being bonded, allowed to dry for a manufacturer recommended amount of time, and then bonds instantly when united. Little or no clamping is needed.
As it says in the Backstage Handbook, "Wait until the green glue turns blue"