The electronic spectrum of alizarin (AZ) in methanol solution was measured and used as reference data for color prediction. The visible part of the spectrum was modelled by different DFT functionals within the TD-DFT framework. The results of a broad range of functionals applied for theoretical spectrum prediction were compared against experimental data by a direct color comparison. The tristimulus model of color expressed in terms of CIE XYZ and CIE Lab parameters was applied both to experimental and predicted spectra. It was found that the HSE03 method along with the 6-31G(d,p) basis set provides the most accurate color prediction, much better than other commonly used functionals such as B3LYP, CAM-B3LYP or PBE0. Besides, the influence of potential errors, introduced by theoretical predictions on color estimation, was examined for different wavelengths. The obtained results showed that color prediction is significantly dependent on the type of basis set and functional applied. The proposed methodology provides a simple, straightforward and more reliable way of theoretical protocols validation than just a comparison of experimental and estimated values of maximum absorbance wavelength. Introduction Color characteristic of many industrial and commercial products is one of those crucially important parameters that require standardization as well as reproducibility. However, tint perception is a complex human activity involving physical, physiological and psychological counterparts.1 The theory of color perception suggests that existing three channels, responding in an antagonist way, are specialized for detection of color vision with non-uniform sensitivity in short (420–440 nm), middle (530–540 nm) and long (560–580 nm) wavelength ranges. The existence of such three distinct cone cells stands for the principle that three parameters are sufficient for quantification of human color sensation. This forms the basis of so called tristimulus values and the defined standard created by the International Commission on Illumination (CIE) in 1931.2,3 A method for associating tristimulus values with perceived color is termed as color space. Thus, the XYZ tristimulus values represent the reflectance or transmittance spectrum weighted by color-matching functions and integrated over the whole spectrum. In Fig. 1 the filtering of the D65 illuminant by absorbance of alizarin
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