Warning: These images may affect your vision for days or even months if you look too long. The damage isn’t irreparable, though, and the worst possible side effect is that you might start seeing colors a little differently, the Indy100 notes.

It’s called the McCollough effect—named after psychologist Celeste McCollough Howard—and one of the earliest studies of this phenomenon dates back to 1975. Researchers separated 16 people into five groups and showed them two different striped patterns featuring the colors red and green.

After looking at each image for about three minutes, the test subjects then stared at black and white striped grids. That’s when the effect started to set in, and participants reported seeing a pinkish hue in the black and white images. One test group reported that the effect remained in full force after five days, while the other four groups said they still felt a weakened form of the effects three months later.

An earlier study from 1969 found that only the colors green and red produced this effect. There’s no consensus on what causes it, but some scientists believe it’s related to neurons in the visual cortex, according to IFL Science. Others have suggested that the brain tries to “color-correct” what you’re seeing, while a third theory posits that the effect is a symptom of withdrawal caused by the absence of color.

To get your vision back to normal more quickly, it’s recommended that you stare at the two images of the red and green lines, except with the image turned 90 degrees counter-clockwise.

[h/t Indy100]