According to graph theory, in order to color any map so that 2 touching regions don't have the same color, 4 distinct colors are enough.
Can somebody color the following map?
Puzzling Stack Exchange is a question and answer site for those who create, solve, and study puzzles. It only takes a minute to sign up.Sign up to join this community
7 is surrounded by 3 squares that all touch, so they are each one of the four colours.
Let us mark them as
7: Red, 6: Blue: 2: Green, 1: Black
1,2, and 6 all border 3, so 3 is Red. 1,3,6 all border 8, so 8 is Green. 4 is then Blue, and 5 is Red. 6,3,8 border 9, so 9 is Black.
Red: 3,5,7; Blue: 4,6; Green: 2,8; Black: 1,9