Colored light is applied in medicine in the treatment of various diseases. The aim of this study was to investigate potential effects of exposure to blue and red light on brain and muscle blood volume ([tHb]) and tissue oxygenation (StO2) measured by noninvasive near-infrared spectrophotometry (NIRS). Ten healthy volunteers were included in a randomized crossover study. Blue light exposure leads to decreased oxygen consumption in the brain and the skeletal muscle. Blue and red light have significantly different effects on [tHb] and StO2.