from machine import Pin
from time import sleep

red =Pin(2,Pin.OUT)
yellow = Pin(4,Pin.OUT)
green = Pin(6,Pin.OUT)

while True:
    red.on()
    sleep(1)
    red.off()
    yellow.on()
    sleep(1)
    yellow.off()
    green.on()
    sleep(1)
    green.off()