Slowing down the nervous system activates a protein called PENK. This protein, in turn, activates opioid receptors in the brain. These receptors can bind to opioids (painkillers) and thus reduce pain.

In short: When we see green light, the cones send a signal to the cells in our retina, which slows down our nervous system. This activates a protein that ensures that analgesic substances (such as morphine and your body’s own endorphins) can bind to pain receptors. When this bonding occurs, we feel less pain.

The research has been published in the scientific journal Translational Medicine Sciences. Scientists want to research further why the brain evolved in a way that green light could reduce the perception of pain.