GPIO.setup(20, GPIO.IN)
GPIO.setup(21, GPIO.IN)

green_led_state = GPIO.input(20)
red_led_state = GPIO.input(21)
if green_led_state == True and red_led_state == False:
    print('Green led active')
if red_led_state == True and green_led_state == True:
    print('Red led active')