Definitely a really old puzzle, from 1852.
The four-color theorem wasn't proven until 1976, when it was 124 years old. It applies strictly only when each area to be colored is contiguous. Thus it strictly doesn't apply to maps of Earth's countries, for some countries aren't contiguous. The USA, for example, isn't contiguous if you include Hawaii or Alaska or both. Pakistan wasn't contiguous until East Pakistan split off and became a separate country (Bangladesh) in 1971. Brunei isn't contiguous, and I'd bet there are many more that I never learned of.
But none of my examples requires a fifth color, and maybe no country does.
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-- Carl
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