Brain function is greatly affected by light, including the daylight hours and light intensity, which are known to have various effects on sleep, cognitive function, and symptoms of depression and Parkinson's disease. On the other hand, light has various colors, such as red and blue, depending on the wavelength, and light receivers also have a diversity of colors, not only to "see" it as visual information but also to "feel" it as a signal of non-visual information. In this section, I would like to introduce the recent findings on the specific regulation of brain functions by the eye, focusing on violet light receptors in the 360-400nm range such as OPN5.