Your current thermostat is compatible with any of the Nest thermostats.
Green - G to G
Blue - C to C
Red - R to Rc or R
Yellow - W1 to Y1 or Y (jumper to Y not needed)
Orange - O to OB or */OB
White - W2 to W2/AUX or W (set as AUX heat)
THe "or" is for the Google Nest Thermostat