In museums, polychrome artworks are highly sensitive to light. They are incredibly vulnerable to irreversible permanent photochemical damage, such as fading and discolouration caused by radiation from light sources. At the same time, such artworks need light sources with excellent colour rendering ability. Therefore, museum lighting sources have dual needs for protection and viewing. For light sources, correlated colour temperature (CCT) is a crucial index, and there are problems such as inconsistency of standards and lack of accuracy. In this work, ten kinds of narrow-band light sources were used to irradiate 17 kinds of pigment samples of polychrome artworks for 1440 h. The colour parameters were measured every 240 h to calculate the colour difference. Based on the data analysis, the law of colour damage of pigments under different narrow-band light sources was obtained, and the damage response function of pigments to different wavelengths of the spectrum was established. By screening the 610 spectra obtained by exhaustively fitting ten kinds of narrow-band spectra, 9477 spectra which meet the visual requirements were left. Combining the response function and spectral distribution, the relative damage values of the 9477 spectra to pigments were calculated, and the relationship between the relative damage value of pigments and the spectral CCT was obtained. It is proposed that 3100 ± 50 K is the CCT range with the lowest average damage to polychrome artworks. Moreover, a method for calculating the recommended CCT of precious polychrome artworks was given.
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