"Blue tends to cause more discomfort and disability glare than other, longer wavelengths," said Dr. David Sliney, an expert on the harmful effects of bright light sources at the U.S. Army Center for Health Promotion and Preventive Medicine in Maryland.We're apparently also more sensitive to blue light in the dark, so blue LEDs may be especially inappropriate for home theater equipment and bedroom PCs. At least one company is developing low-intensity blue LEDs, but maybe it's time for a red or green revival.
Sliney said the eye's lens cannot focus sharply on the blue lights. While red or green light is focused precisely onto the retina, blue light is focused slightly in front of it, which causes a distracting halo around bright blue lights.
In addition, blue scatters more widely than other colors as it passes through the eyeball, Sliney said. Together, these two effects cause the intense blue light from a point source, like an LED, to spread out across the retina, interfering with other parts of the scene. It's called dispersion: Blue's shorter wavelength makes it refract at a greater angle than, say, red or green.