Nest Thermostat Wiring Colors

Can't figure this 3 wire system out or find anything in postal about it Nest learning thermostat wiring diagram Thermostat wiring wire heat color diagram air pump nest guide common goodman colors honeywell code heater aruf handler wires labels

Nest Learning Thermostat Wiring Diagram

Nest thermostat wiring diagram

Can't figure this 3 wire system out or find anything in postal about it

Nest Learning Thermostat Wiring Diagram