I Need To Know Witch Wires To Hook Up From The Ac To The Thermostat Since They Do Not All Match In Color.

I Have A 3 Ton Carrier Ac.the Wires For The Thermostat From The Ac Are
Light Green
Yellow
Tan
Orange

The Thermostat Hookups Are
W
Rh
Rc
Y
G
A
It Also Has A Wire That Says" Y "for Gas Heat
"a" Is For Electric Heat

The Wire Is Hooked To "y" ,when I Bought It New

I Am Only Hooking Up The Ac Unit To This Thermostat. Not Any Heat.
Please Help.

Were all those wires hooked up before and to where? I would say light green will go to the "G" terminal Yellow wire to the "Y" terminal and you need to figure out which of the orange and tan has 24 volts whichever does needs to go to the RC terminal.