I currently have a 4 wire Coleman thermostat it has yellow wire hooked up to the R terminal , white wire hooked to the Y terminal, red wire hooked to a red wire unmarked, and then a green wire also unmarked, there is a blue wire in the wall that is capped off and not in use. The Coleman thermostat is model 7900-7541 controlling a Coleman EB12B furnace and air conditioner. Im wanting to know what letter the red and green wire need to be hooked to on the Honeywell it is model CT8602 and also wondering if the blue wire will be needed for this thermostat, THANKS for any help in advance

Here is your instruction from Honeywell.

http://customer.honeywell.com/techli...0s/69-1532.pdf

You will need to follow the colored wires that you have now back to the furnace to see where they are hooked up to and then you will know where to hook them at the new thermostat.

Usually people follow a color code but I see in your case it may not have been followed.
There is more info on thermostat wiring at the beginning of this board under sticky notes.