Research conducted by Choi and team confirms that experiencing cooler light is energizing. They “investigated physiological and subjective responses to morning light exposure of commercially available LED lighting with different correlated colour temperatures to predict how LED-based smart lighting employed in future learning environments will impact students. . . . university students underwent an hour of morning light exposure to both warm (3,500 K) and blue-enriched (6,500 K) white lights at recommended illuminance levels for classrooms and lecture halls (500 lux). The decline of melatonin levels was significantly greater after the exposure to blue-enriched white light. Exposure to blue-enriched white light significantly improved subjective perception of alertness, mood, and visual comfort. . . . Blue-enriched LED light seems to be a simple yet effective potential countermeasure for morning drowsiness and dozing off in class, particularly in schools with insufficient daylight.” People in the bluer light thus felt significantly more alert, etc., than those experiencing the warmer light.
Kyungah Choi, Cheong Shin, Taesu Kim, Hyun Chung, and Hyeon-Jeong Suk. “Awakening Effects of Blue-Enriched Morning Light Exposure on University Students’ Physiological and Subjective Responses.” Scientific Reports, vol. 9, article 345, DOI:10.1038/s41598-018-36791-5