The main objective of this paper is to investigate the possibility of evaluating the color changes in real photovoltaic modules from reflectance measurements. To accomplish this main objective, the work has been organized into three main axis: (1). Exploring the possibility of using simplified instrumentation and techniques for the measurement of color parameters in solar cells. (2). Identifying a simple parameter as an indicator of solar module color appearance and (3). Exploring the possibility of correlating that parameter with solar module degradation. It is explored the use of reflectance and related magnitude Yellowness Index (YI) as an indicator of photovoltaic (PV) solar module surface color change and degradation. While spectrometric quantities as transmittance have been used as a measurement of separated encapsulant and backsheet characteristics, in the present paper reflectance of the surface of real PV solar mono and polycrystalline modules are analyzed. With the objective of verifying the applicability of such measurements in real PV installations, the correctness of using simplified measurement geometries and portable spectrometers is tested. It is found that 45 degrees/45 degrees and hemispheric reflectance supply similar results. Consequently portable fiber optic spectrometers and simple fiber optic probes with their holders can be used. We found that 45 degrees/45 degrees and hemispheric reflectance with their associated Yellowness Index can be used indistinctly in the cases analyzed as a good indicator of superficial color changes. We have also concluded that Yellowness Index is a good indicator of changes in appearance in PV modules. It is observed an increase of Yellowness Index with ultraviolet dose supplied to a solar module and a reduction in its maximum power.