The Hazardous waste drop off may not accept liquid paint in the future-
In some parts of the country, there are recyclers who filter, mix, and colorize leftover latex paint. (There's a big program of this type in Seattle -- King County WA, for instance.) I don't know whether there are any in this area. But I do know that "The Second Mile Center" will accept partially used cans of paint for resale (220 S 45th -- between Locust & Walnut). I think that the Toviah Thrift Shop (4200 block of Chestnut, north side) will also take this commodity. In either case, before dropping it off, you should verify that it's still usable (water in limited amounts can be added to latex paint if it starts to get thick) and also be sure that the color is somehow shown on the outside of the can.
Al Krigman