I have a Lennox 67K4801 /AAT89B38G1 Thermastat with the following connections:

O- ORANGE
G- GREEN
Y1- YELLOW
R- RED
C- BLUE
W1- WHITE

I am installing a Honeywell RTH7500 Thermostat. The guide has the following.

C- BLUE
G- GREEN
Y- YELLOW
W- WHITE
RC
R- RED
W2
Y2
So where do I install the orange wire ?