from machine import Pin
import time

# setup
button = Pin(4, Pin.IN, Pin.PULL_UP)

blue = Pin(17, Pin.OUT)
green = Pin(18, Pin.OUT)
red = Pin(19, Pin.OUT)

state = 0   # 0=blue, 1=green, 2=red
last_button = 1

while True:
    current = button.value()

    # detect button press (when it changes from 1 to 0)
    if last_button == 1 and current == 0:
        state = state + 1

        if state > 2:
            state = 0

        time.sleep(0.2)  # debounce

    last_button = current

    # control LEDs based on state
    if state == 0:
        blue.on()
        green.off()
        red.off()

    elif state == 1:
        blue.off()
        green.on()
        red.off()

    elif state == 2:
        blue.off()
        green.off()
        red.on()