from typing import Tuple


def parse_optional_alpha(colour) -> Tuple[int]:
    if not isinstance(colour, (list, tuple)):
        raise ValueError("Unknown colour info.")

    if len(colour) not in (3, 4):
        raise ValueError("Unknown colour info.")

    try:
        r, g, b, a = colour
        return (r, g, b, a)
    except ValueError:
        return (*colour, 0)


def normalise_colour_info(colour):
    """Normalise colour info to (name, (r, g, b, alpha))."""

    if len(colour) >= 3:
        try:
            return ("", parse_optional_alpha(colour))
        except ValueError as e:
            raise e

    try:
        name, values = colour
    except ValueError:
        raise ValueError("Unknown colour info.")

    return (name, parse_optional_alpha(values))


assert normalise_colour_info(("a", (1, 2, 3))) == ("a", (1, 2, 3, 0))
assert normalise_colour_info(("a", (1, 2, 3, 4))) == ("a", (1, 2, 3, 4))
assert normalise_colour_info((1, 2, 3, 4)) == ("", (1, 2, 3, 4))
assert normalise_colour_info((1, 2, 3)) == ("", (1, 2, 3, 0))