Chromotherapy is based on the effect of colored light with different frequencies on human neurohormonal pathways, precisely on melatonin and serotonin pathways in brain. There is evidence that visible electromagnetic spectrum of light we see as colors can have impact on human health, Cicardian rhythm or biological clock is complex fundamental physiological and biological cycle in human organism. The biological clock in humans is located in the specialized group of brain cells called suprachiasmatic nucleus (SCN) within the anterior hypothalamus. The complex process of neurohormonal regulation of cicardian rhythm in humans is essential for synchronized interaction and coordination of internal body function with the environment. Given these facts it is clear that any shift in cicardian rhythm results in neurohormonal imbalance which consequently could lead to various psychiatric disorders affecting humans. Studies on sleep disorders, depression, seasonal affective disorder (SAD) and post-traumatic stress disorder (PTSD) suggested that symptoms, signs, and biologic markers associated to these psychiatric disorders are due to marked alterations in melatonin and serotonin levels. The main hypothesis of chromotherapy is that specific colors of the visible spectrum are activators or inhibitors of complex physiological, biological and biochemical processes in human brain such as synthesis of various neurohormons. According to all previous findings, our goal is future investigation of the effect and possible application of chromotherapy in the complementary psychiatric treatment in patients with diagnostic criteria which are clearly related to melatonin and serotonin disturbances.