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ICOM-CC Metal 2022 September 5-9, 2022 Helsinki, Finland, One of the most obvious signs of metal corrosion is color change. This phenomenon could be used to assess the corrosivity of the indoor environment in museums and collections in other institutions. The MIPAC project is therefore developing a preventive conservation tool for monitoring the impact of the indoor environment on cultural heritage materials, based on the color changes associated with deterioration. The changes are assessed by analyzing photographs taken with cell phones and provided by museum visitors and staff through an app. A color reference chart was designed, in which metal coupons are used as dosimeters. CIELAB color coordinates are extracted from the images and adjusted using the color references with a calibration algorithm. This approach allows the preventive conservation of cultural heritage from both a scientific-technological and a social perspective, since it involves public participation in the conservation of museum collections. However, for this monitoring approach to be valid, the correlations between color change and corrosion extent need to be determined in order to explore the possibilities of quantifying the extent of corrosion from the calibrated photographs. This paper presents the preliminary results of a validation study, based on tests of a series of copper and silver coupons exposed in museum showcases for 6, 12, and 18 months. Color and corrosion extent measured by gravimetry and galvanostatic reduction showed the good correlation between some of the colorimetric information and the corrosion thickness. Although the uneven distribution of surface corrosion complicates the establishment of a correlation between corrosion and color change, this issue can be tackled by a localized evaluation of the corrosion obtained by electrochemical reduction.