import board
import neopixel
import time
led = neopixel.NeoPixel(board.D8, 10, 
    brightness=0.3, auto_write=False)
negro = (0, 0, 0)
rojo = (255, 0, 0)
naranja = (255, 64, 0)
while True:
    for k in range (10):
        led.fill(negro)
        j = k - 1
        if j < 0:
            j = j + 10
        led[k] = rojo
        led[j] = naranja
        led.write()
        time.sleep(0.15)