Hello, I purchased a home with a programmable Honeywell Thermostat Model RTH 7500D, however, the previous tenent took everything off the walls one of which is the thermostat. I can put it back but the wires are exposed and have no idea on what letter on the connector to install etc. I have four wires exposed: White, Red, Blue, and Red... The Thermostat letters: C, G, Y, O/B, RC, R, W, L, E, and AUX... Can you please tell me to what leters the color wires get connected to?

Look on the inside unit where the thermostat wires go and see what color goes to what letter terminal on the inside unit. Then use that color to go to the same letter terminal on the new thermostat. That is as best that can be done with your situation from here.