Inhibitory effect of light of different wavelengths on the fall of core temperature during the nighttime.

Nocturnal core temperature fall was significantly inhibited by green, blue, and red light exposure with 1,000 lx from 21:00 h to 02:00 h. The core temperature in red became identical from that in control during the following sleep period, but not in green and blue. These findings are discussed in terms of urinary melatonin behavior.