Various pigments are characterized by determination of parameters S (backscattering) and K (absorption) as functions of wavelength in the solar spectral range of 300–2500 nm. Measured values of S for generic titanium dioxide (rutile) white pigment are in rough agreement with values computed from the Mie theory, supplemented by a simple multiple scattering model. Pigments in widespread use are examined, with particular emphasis on those that may be useful for formulating non-white materials that can reflect the near-infrared (NIR) portion of sunlight, such as the complex inorganic color pigments (mixed metal oxides). These materials remain cooler in sunlight than comparable NIR-absorbing colors. NIR-absorptive pigments are to be avoided. High NIR reflectance can be produced by a reflective metal substrate, an NIR-reflective underlayer, and/or by the use of a pigment that scatters strongly in the NIR.

Ronnen Levinson, Paul Berdahl, Hashem Akbari, Solar spectral optical properties of pigments—Part II: survey of common colorants, Solar Energy Materials and Solar Cells, Volume 89, Issue 4, 2005, Pages 351-389, ISSN 0927-0248, https://doi.org/10.1016/j.solmat.2004.11.013.