How to hook up the colored wires to a honeywell rth7400 thermostat? It is for a trane heat pump.

Hook them up exactly like the directions that came with your new thermostat says to hook them up. You will also have to refer to the way they were hooked up to the old thermostat. The directions tell you to write down or label where the wires were located on the old thermostat. The color of the wires is not as important as where they were located on the old thermostat since many times the colors can actually mean different things on different thermostats and that is why it is important to label them before removal. If you did not do that then you will have to go to the unit inside and write down all the letters with the corresponding colors and post the entire list here for us to be able to help you at all. Hooking the wrong wires to the wrong locations can be damaging to the new thermostat and the equipment.

Also please post the exact brand and exact model number of the old thermostat to help with the locations for the new one.