Blue light in the Mars500 habitat was used to test certain aspects of spaceflight to Mars. In 2011 six people from China, Russia and Europe spent 520 days in isolation in a mock spacecraft, the time it would take to fly to Mars and back. They did not exit the habitat nor see the Sun or breathe fresh air, just like on a real spaceflight.
Aside from many psychology experiments, one experiment looked at how lighting could influence crew sleeping patterns as well as prepare their eyes for seeing real daylight at the end of their mission.
Morning and evening sunlight on Earth has more red in it, while bright sunlight during the day has more blue wavelengths, cueing our body for the time ahead. Blue lighting could influence the body to be more alert, whereas red lighting might induce sleep.