thermostat
I am installing a smart thermostat but I found the old thermostat has the green and red wires both running to the g terminal. When installing the new thermostat I will be removing the jumper wire between RC & RH. I do not have a heat pump ac unit only I live in south FL.
I've labeled your photo, which should help you understand what's going on.
What you describe as a "blue" wire at the thermostat, you describe as "gray" at the air handler. I can't be sure, since I'm not there, but I think they are one in the same.
If you want to install a fancy new WiFi thermostat, you're going to have to pull an additional wire from the air handler to the thermostat. Once you have that, you'll connect one end to the C terminal of the air handler, and the other end to the C terminal of the thermostat.
You should connect the C wire, from whichever unit supplies the R wire. Typically it's the air handler, but since you've given no details it's impossible to say for sure.
Best Answer
If you look very closely you'll see the red wire is on R and the green wire is on G. It just looks like the red and green are tied together on G.