def adjust_colour_brightness(rgb, factor):
    """
    Clue is in the name.

    Parameters
    ----------
    rgb : tuple
        (Red, Green, Blue)
    factor : Percentage Adjust
        Amount to change brightness by.

    Returns
    -------
    tuple

    """
    return tuple([value + 255*max([0, factor])-abs(factor*value) for value in rgb])