def wheel(pos):
    """b->g->r color wheel from 0 to 1020, neopixels use grb format"""
    
    if pos < 255:
        return [0 , pos , 255]
    elif pos < 510:
        pos -= 255
        return [0 , 255, 255 - pos]
    elif pos < 765:
        pos -= 510
        return [ pos, 255, 0]
    elif pos<=1020:
        pos -= 765
        return [255, 255 - pos, 0]
    else:
        return [255, 0, 0]