Count the colors. You probably count four: magenta, cyan, orange, and green.
There are in fact only three colors. What you’re seeing as cyan is actually the same green. This trick uses a technique called retinal mixing, which exploits color’s natural tendency to react to other colors. The color we think we see is entirely dependent on its surrounding colors. In this example, your eye is pulling blue from the surrounding magenta, making the green seem bluer than it is.
We saw this done a lot in the sixties in schemes we loosely refer to as “loud” or “clashing” colors. Far out.