Billboard advertising needs to be different and original to get attention. Erecting what appears to be an enormous plain canvas certainly generates intrigue, but what’s the message? Well, it turns out that a specific target audience will see more in this ad than others.

To onlookers with standard color vision, the billboard looks like a bit like a magic eye picture made up of green dots. But no matter how long they look at it, the hidden message won’t appear because it’s only visible to people with colour blindness.