We have studied the differences in the reflectance spectra between various samples of lichen thalli plain (Pseudevernia furfuracea). We have compared the reflectance spectra of the dry and wet lichen thalli in the range of 280 nm to 887 nm. We have determined the contents of chlorophylls and carotenoids and compared them between the samples of dry and wet thalli. We have also tested the differences in the concentration of chlorophyll a and b and carotenoids between dry and wet lichen thalli, trying to determine the correlation between the colour reflectance spectral bands and biochemical parameters. The results have shown that the reflectance spectra of wet thalli have all the typical characteristics of a healthy active thalli, while the reflectance spectra of the dry thalli gradually rise to the NIR spectrum and then decline. The reflectance spectra of the wet thalli have a relatively low reflectance in the UV range. Its highest point is in the green belt at 560 nm. We have found that the dry and wet samples of thalli were statistically significantly different in the concentration of chlorophyll a and carotenoids. The relationship between the colour reflectance spectral bands and the biochemical properties have not been proved. We have only been able to prove the influence of chlorophyll a and carotenoids on the NIR spectra in wet lichens.