Migraine sufferers may no longer have to retreat to a dark room after experts found that green light could ease their misery.
Those with intense headaches - often accompanied by nausea and light sensitivity - tolerate "pure" green better than other colours, scientists discovered.
In tests, it even reduced pain for about one in five people. Now experts are developing a lightbulb to emit the light - as well as sunglasses that block other colours.
The US study compared 69 patients' reactions to blue, amber, green and red light. Some 80 per cent felt worse subjected to all colours bar green - which worsened symptoms for just 40 per cent.
Dr Rami Burstein, of the Beth Israel Deaconess Medical Center in Massachusetts, said: "These findings offer real hope to patients with migraines and a promising path forward for researchers and clinicians."
Migraines affect one in four women and one in 12 men and lead to more sick days than any other illness.