4 color theorum

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It's impossible to it with 3 colors. Any state that touches an odd number of other states in a normal way (the four corners area is a special case), and isn't at an edge of the country, for example Nevada, requires 3 colors other than its own for its neighbors.

[○∙◄☻¥tπ[╪AV┼cVê└]

some researchers at the University of Illinois-Champaign, actually wrote a proof for that 4 colors is all you need to make a map with no two of the same colors touching, however the proof is more than 600 pages long and a good 60 pages of that is proofs of other proofs they used in the big proof, and would no doubt be boring as hell to analyze.

The original proof was really really ugly. Someone else came up with a merely reall ugly proof.

http://www.math.gatech.edu/~thomas/FC/fourcolor.html#References