Comparisons of REFF curves (a) and normalized color ratio curves (b) for the CE5 sample measured using the three-color goniometer and the spectro-goniometer. In panel (b), the blue curves represent measurements from the three-color goniometer at four incident zenith angles (i = 0°, 30°, 45°, and 60°), while the orange curves represent measurements from the spectro-goniometer at two incident zenith angles (i = 30° and 45°). All curves are normalized to 1 at their respective minimum phase angles: 3° for the three-color goniometer and 10° for the spectro-goniometer.