The four-color theorem states that any map in a plane can be colored using four-colors in such a way that regions sharing a common boundary (other than a single point) do not share the same color.
Martin Gardner wrote a popular account of what was known at the time about the four color theorem in his September 1960 Mathematical Games column in Scientific American magazine. In 1975 Gardner revisited the topic by publishing a map said to be a counter-example in his infamous April fool's hoax column of April 1975.
If you use 4 colors to color any kind of picture, it would not touch the same color with neighbors
I used green, red, blue, yellow. And neighbors doesn't touch the same color.
This picture used blue, green, yellow, red. It doesn't touch same colors each other
