Light is a condition that human beings are subjected to in nature. Light is not only a physical parameter but also an important factor, which is affecting the mental and cognitive performance of the person. For this reason, in recent years, many researchers and scientists have been working on and exploring this direction of light. The spectral structure of light in the natural environment shows a continuous change. We can define this natural environment as the spectral transformation of daylight in open air. Thus, people who remain in closed environments during the day are living under unfavourable conditions, such as constant colour temperatures and luminous flux of illumination. The studies aimed at reducing this harmful effect the most. These studies are based on the principle that all intermediate colours are obtained by blending the light in 2 different colours (usually one is very warm white and the other is very cold white) and that the intermediate colours are timed within a certain scenario and illuminated indoors to simulate the outside environment. In this study, the mixture of light sources in different colours was mathematically modelled in computer environment and the CCT in K of the mixture was calculated. It is also optimized to obtain the mixture colour with least mistakes of the mixture functions by comparing with the actual measurement results.