def colourfulness_correlate(F_L, C_94):
    """
    Returns the *colourfulness* correlate :math:`M_94`.

    Parameters
    ----------
    F_L : numeric
        Luminance adaptation factor :math:`F_L`.
    numeric
        *Chroma* correlate :math:`C_94`.

    Returns
    -------
    numeric
        *Colourfulness* correlate :math:`M_94`.

    Examples
    --------
    >>> F_L = 1.16754446414718
    >>> C_94 = 0.12105083993617581
    >>> colourfulness_correlate(F_L, C_94)  # doctest: +ELLIPSIS
    0.1238964...
    """

    M_94 = F_L ** 0.15 * C_94

    return M_94