def METHOD_NAME(self):
    vega = Vega.from_default()
    with vega_fluxd.set({
            'V': -0.013 * u.ABmag,
            'V(lambda eff)': 5476 * u.AA,
            'I': 0.414 * u.ABmag,
            'I(lambda eff)': 7993 * u.AA
    }):
        lambda_eff, ci = vega.color_index(('V', 'I'), u.ABmag)
    assert np.allclose(lambda_eff.value, [5476, 7993])
    assert np.isclose(ci.value, -0.427)