Gilles Vandewalle at the University of Liège, Belgium, Howard Cooper at the French National Institute of Health and Medical Research in Bron and their colleagues exposed 16 volunteers to blue, green or orange light for 10 minutes, then kept them in darkness for 70 minutes. The researchers recorded the volunteers' brain activity while the participants performed various cognitive tests under green light. People exposed to orange light had more activity in the prefrontal cortex, which is involved in higher cognitive function, than those exposed to blue light.