Polarized reflectivity spectra versus temperature of two isostructural charge-transfer salts kappa-(ET)(4)[M(CN)(6)][N-(C2H5)(4)]center dot 2H(2)O (M = Co-III and Fe-III) (ET = bis(ethylenedithio)tetrathiafulvalene) were studied. The electronic and vibrational spectra exhibit a drastic change at around 150 K. On the basis of the spectral analysis, we deduced the nature of the phase transition. The phase transition at 150 K is due to a charge ordering; above this temperature, strong charge fluctuations are observed.