I am replacing a honeywell thermostat. I only have 4 wires coming out of my wall.
Green--wired to the 'C' on the old thermostat
Red----wired to the 'C' on the old thermostat
White---wired to the 'W' on the old thermostat
Black---wired to the 'P' on the old thermostat

I purchased a RTH7500 and don't know what I need hook the wires to..