Extended duration work schedules and nighttime operations are associated with impaired performance, reduced alertness and mood, and increased sleepiness and risk of accidents. Appropriately scheduled light/dark exposure is a powerful means of resetting the human circadian pacemaker. Bright light has been used in various clinical settings to induce physiologic adaptation in individuals suffering from circadian rhythm disorders (e.g., night shift workers, people with Advanced and Delayed Sleep Phase Syndromes). Properly timed exposure to bright light can produce rapid physiologic adaptation of the circadian pacemaker to a single week of night work and facilitate rapid entrainment to a rotating work schedule, as well as enhance the alertness of night workers during their work shifts. Advanced and Delayed Sleep Phase Syndromes (ASPS and DSPS, respectively) are characterized by a marked difficulty in maintaining appropriate timing of sleep during the desired hours, and there is evidence suggesting that circadian misalignment may underlie the pathophysiology of this condition. We and others have reported data from clinical studies that suggest evening exposure to bright light or early morning exposure to bright light are successful in the treatment of ASPS or DSPS, respectively. The current study was designed to evaluate the effectiveness of shorter wavelength light exposure over intermediate and longer wavelength light as a countermeasure for circadian misalignment. The findings highlight the need for further development of effective and energy-efficient methods for treatment of circadian rhythm disorders. Optimizing the wavelength of light holds the potential for producing shorter, more efficient light treatment regimens. Shorter treatment regimens would not only increase compliance in clinical populations, but would make light treatment more practical in industrial/work settings. This lighting countermeasure could be beneficial for those on Earth who work extended duration overnight shifts or other unusual schedules and may negate the effects of fatigue on work performance.