If you have to have light at night, a new study suggests that the color can make a big difference in how (un)healthy it is - and the answer is counter-intuitive.

Though the color blue is believed to have a calming effect, a study involving hamsters found that blue light had the worst effects on mood-related measures, followed closely by white light. The best? Red.  

Hamsters exposed to red light at night had significantly less evidence of depressive-like symptoms and changes in the brain linked to depression, compared to those that experienced blue or white light. Total darkness is still best.

"Our findings suggest that if we could use red light when appropriate for night-shift workers, it may not have some of the negative effects on their health that white light does," said Randy Nelson, co-author of the study and professor of neuroscience and psychology at The Ohio State University .

The research examined the role of specialized photosensitive cells in the retina -- called ipRGCs -- that don't have a major role in vision, but detect light and send messages to a part of the brain that helps regulate the body's circadian clock. This is the body's master clock that helps determine when people feel sleepy and awake.

Other research suggests these light-sensitive cells also send messages to parts of the brain that play a role in mood and emotion.