*2.3. Visible Reflectance*

The visible reflectance measurements have been carried out by a portable spectrometer CM-700d produced by Konika Minolta. The spectrometer is equipped with an UV radiation filter Xenon lamp and a silicon photodiodes array detector. The analysis range is 400–700 nm with a slit of 10 nm. Illumination area: 8 mm<sup>2</sup> , Observer: 10, Illuminant: D65, measurement conditions: SCI (SCI/SCE, illumination/acquisition geometry), number of averaged acquisitions: 5. We performed at least 4 acquisitions for each point.
