def get_colour_set(n_colours, rng):
    """
    Generates a (unique) list of randomly generated RGB colours.

    # Arguments:
        n_colours: the number of colours to generate.
        rng: an instance of numpy.random.Generator.

    # Returns:
        colours: a list of randomly generated colours.
    """
    colours = []

    for _ in range(n_colours):
        cand = None

        while cand is None or cand in colours:
            cand = (rng.uniform(), rng.uniform(), rng.uniform())

        colours.append(cand)

    return colours