Strictly speaking this "visual proof" is not a proof at all, it's just an illustration of one simple case. But what's good about is that it helps give you an in

Strictly speaking this "visual proof" is not a proof at all, it's just an illustration of one simple case. But what's good about is that it helps give you an intuition about why Ramsey's theorem is true: namely, that you'd eventually run into a dead-end when trying to color edges, in the sense that you're bound to create a sub-graph where all edges are either colored red or blue.