The resistor should have a power
rating higher than that of the indicator light. Typically, a 20 Watt resistor works well.
Using a 25,000 RPI circuit limits the current
flow (when Reverse Polarity is indicated) to 4.8 milliAmps (120 V ų 25,000 Ω = 0.0048 A); which is just below the tripping threshold of U.S. Ground Fault Circuit Interrupters (GFCIs trip @ 5 mA),