I have 4 wires a red, blue, green and white from my old thermostat. A friend of mine told me to cross up the white and red to temporarily get the heat running. I got the Honeywell RHT221b, but am not certain where the red or the white go? In the old one the White went to R and the red to O. The honeywell doesn't have an O or plain R option.

What type of a system do you have?