2002 Mercury Mountaineer Florescent green

What you're seeing is a leak-detecting dye that someone added to the refrigerant. If that is coming from right behind the pulley and clutch assembly, the front seal must be replaced. If it's coming from one of the service ports, be sure the cap is on and that it's tight. Those ports have valves that typically leak. Their only job is to hold the refrigerant in while you remove the service hose and install the cap.