def norm_colour(colour):
    """Normalises a colour from it's 255 rgba values to values between 0 and 1.

    Arguments:
        colour -- a list representing an RGBA colour.

    Returns:
        A tuple of length 4 representing an  RGBA colour where  each element has
        been scaled from 0-255 to 0-1.
    """
    return (colour[0]/255., colour[1]/255., colour[2]/255., 1.)