•Lightness evaluation in specimens treated with TiO2 in the long term.•TiO2 effect on light radiation of coating mortars.•Aesthetic perception maintenance of facades treated with TiO2.•Solar absorption on surfaces treated with TiO2.•The color difference on surfaces treated by TiO2. The importance of colours is not limited to the aesthetic but also other parameters like thermal comfort. Painting light colours on the building's external surfaces increases its reflection of solar radiation, reducing the heat gains. In contrast, dark colours can increase solar heat gains by absorbing more radiation. Regarding the TiO2 answer to the lightness on the facade, different samples of TiO2 were tested. First, in the laboratory for methylene blue dye degradation and second in a natural environment using different forms of treatment (powder and suspension) on mortars, measured by a spectrophotometer over three years to determine the loss of lightness over time. The methylene blue test showed that the TiO2-P25p, TiO2-PC-S7s, and TiO2-E502s samples had the same effectiveness after exposure to artificial UV radiation, while the TiO2-PC105p sample presented the worst performance. Concerning the lightness, after thirty-seven months of the natural exposition, the white painted specimens had the best results than specimens with TiO2 suspensions and specimens with TiO2 in powder. Beyond the absorptivity, the white painted specimens could be considered with low absorptivity. In contrast, the specimens treated with TiO2 suspension and those treated with TiO2 powder could be medium absorptivity. Regarding the visual aesthetic perception, the study concludes that for the final user, there is no great difference in white painted specimens, while for the other (powder and suspension), the colour difference can be noticed well over three years of exposure.