I've been learning to make optical illusions. It started when I got fascinated by this piece by Akiyoshi Kitaoka. There are no red pixels in these strawberries, which is sort of nuts. I put it in Illustrator, to find out how it all worked, by sucking out swatches.
Based on what I learned, I made my own illusion. Some people in the comments were suggesting the effect only works because we are used to seeing strawberries as red. But that's not right. It works because of Additive Colour Change. I made one with sneakers.