Green light therapy is no better than red light for treating adolescents and young adults with delayed sleep-wake phase disorder, according to researchers from Australia, reports Psych Congress Network.

Whether morning activity could improve outcomes remains unclear, they report in Sleep Medicine, online February 9. “It was most surprising to find that there were no differences in treatment based on whether green or red light was administered in bright-light therapy,” said Dr. Cele Richardson from Flinders University, in Adelaide.

“There is convincing experimental evidence to suggest that short-wavelength light (e.g., blue-green light) is most effective at shifting circadian rhythms earlier, with relatively little phase shifting occurring in response to long-wavelength light (e.g., red),” she told Reuters Health by email.