def _colorize(t):
    """Convert (r, g, b) triple to "#RRGGBB" string

    For use with ``visualize(color=...)``

    Examples
    --------
    >>> _colorize((255, 255, 255))
    '#FFFFFF'
    >>> _colorize((0, 32, 128))
    '#002080'
    """
    t = t[:3]
    i = sum(v * 256 ** (len(t) - i - 1) for i, v in enumerate(t))
    h = hex(int(i))[2:].upper()
    h = "0" * (6 - len(h)) + h
    return "#" + h