Today, for the needs of modern packaging, digital printing technology has been increasingly used, with the main representatives of Electro photography and Inkjet. Their share in the total value in the graphics industry is 20 %. High-quality multicolor printing in electrophotographic printing requires an additional preparation of the printing substrate to which special colors are printed. In order for the liquid electrophotographic ink to be optimally adhered to the substrate, it is necessary to achieve the ideal substrate surface tension with additional enrichment. To ensure the desired bonding of the ink to the printing substrate, the corona treatment and coating with the liquid for regulating the surface tension are applied. The corona treatment generates surface modification that is manifested in micro roughness resulting in better ink binding. In the case of printing substrates whose surface is uneven, preparatory coating should be applied to improve the surface layer properties. Within the scope of thesis, the research and redefining of the influence of the corona power and the thickness of the applied of surface tension regulation fluids on the quality of multicolor reproduction has been carried out. The HP Indigo WS 6800 electrophotographic printing machine equipped with a Vetaphone corona unit and a 5-cylinder Michelman primer unit, was used in the experiment. As a printing substrate is used a certified art paper Condat 90 g / m2 intended for the realization of high-quality prints. The methods used to detect changes in prints are nondestructive and are based on colorimetry and spectrophotometry These methods allow to determine the differences in the color gamut, the structure of the characteristic screening elements, the amplitude-modulated screening and the increase in the number of multicolored separations, in the printing process itself. Based on the obtained results, the optimal color tones values (Lab and dot gain) with which the higher quality of digital prints is achieved have been determined, leading to the redefinition of the current industry standard for digital printing. Three basic hypotheses have been put in the dissertation. The first hypothesis selectively examines the variation effect of corona power on multi-color reproduction of the HP Indigo printing machine, while the second hypothesis examines the thickness influence of applied fluid for regulation of surface tension on the required print quality. The third hypothesis is most comprehensive and gives a general analysis of the defined sample experiment and correlates them to the existing standard for the graphics industry (ISO 12647-8).The results show that in comparison to the ideal PSD imprint, minimal deviations of the primary colors are: ∆EC(1g/m2_0W) = 1,49; ∆EM(0g/m2_450W) = 2,21; ∆EY(0,5g/m2_0W) = 1,85; ∆EK(0g/m2_0W) = 2,79. Corona treatment will not significantly effect on colour changes of process colors (∆EY = 0,01; ∆EK = 0,55). In the case of these imprints created by overprint, significant color changes are achieved, but still below the visual boundary (∆Emax. = 0,88). By applying the same surface tension regulation fluid (primer), the resulting primary color deviations remain low (∆EC = 0,02; ∆EK = 0,61), with the secondary colors remaining almost unchanged (∆Emax. = 0,29). The obtained results visually do not show any significant color change for the glossy coated substrate. However, bringing them in correlation with other printing parameters (photoreceptor illumination, photoreceptor developing, toner fixation ...) can contribute to the stability of electro photographic press with liquid toner (ElectroInk), which ensures reproduction consistency in areas with different tonal coverage. The type of pigment in ElectroInk dyes and the treatment of printing substrate have different impacts on the realization of the required color results and the resulting tone changes. Cyan ElectroInk color will be the most stable (the slightest color change), while the black ElectroInk color will be significantly more unstable (color changes are visible to the human eye).