def colors_average(colors):
    """Return average color for a set of colors."""
    group_size = len(colors)
    red_sum, green_sum, blue_sum = 0, 0, 0
    for color in colors:
        red_sum += color[0]
        green_sum += color[1]
        blue_sum += color[2]
    red_ave, green_ave, blue_ave = red_sum / group_size, green_sum / group_size, blue_sum / group_size
    return [red_ave, green_ave, blue_ave]