The combination of UV-radiation, moisture and high temperatures influence colours on textiles. An oxidation process.
Many years of research with proffessional aging equipment have led to good light fastness of these fabrics. Natural dyes are however more susceptible to change under the above influences then the best chemical colours. Tinctoria fabrics age gentle. They become slowly lighter without losing their richness in colour.
Direct sunlight should be avoided and lining is necessary.