How many colors do we need to paint all countries in the globe, but with different colors neighbouring?

I'd say 5, using 'blue' for all bodies of water, and four other colors for all different countries. If you want to ignore water and only consider land boundaries, then 4 colors are enough.





In many parts of the globe, you don't need 4 colors for the land boundaries. You could color all of North America from Canada down to Panama with just 3 colors.





When you get into South America, you need 4 colors for the land boundaries. Look at the countries of Argentina, Bolivia, Brasil and Paraguay; each one touches the other three, so they must have 4 distinct colors.





Mathematically, 4 colors are sufficient for any simple map, but the real world isn't necessarily 'simple'. If a single country can be made up of more than 1 piece (e.g. the US with Alaska), then you could dream up a world map that needed 5 or 6 or more colors.





There are no such situations with the real world map as it is now, so 4 colors (or 5 with water) are enough.How many colors do we need to paint all countries in the globe, but with different colors neighbouring?
There's the 4-color theorem, which has been proven by computers (because the calculations are very long and can be done only with help from a computer).





So 4 colors are all you'll need.How many colors do we need to paint all countries in the globe, but with different colors neighbouring?
I believe I've seen that answer somewhere before and if my memory serves me correctly (which it usually doesn't... ) the answer would be 7, as apparently the one country with the most neighbouring countries has 6 neighbouring countries...
Four
4 because some countries border other countries which border another and another and it makes about 4
Obviously, painting each country a different color will solve the problem. But if we're looking for a way to do it in the LEAST amount of colors possible, the answer is 4. This is because of the classical ';Four Color Theorem'; problem of mathematics:


http://mathworld.wolfram.com/Four-ColorT鈥?/a>
I really laughed when I read thuddie's answer he summed it up.
When Britain was `Great`, you see only 1 colour, RED.
The 4-color map theorem proves that the answer is no greater than 4 -- oceans or anything else included. (Technically it only applies to a plane, not a sphere, but given the theorem on the plane it is very easy to derive it also for the actual globe as well.)





So the other part of the problem is proving that the number needed is AT least four, if that's indeed true.





And it's exactly four, since each of France, Germany, Belgium, and Luxemburg has a border with each of the other three.
Two. Blue and Green
The four color map theorem has been proven. You will never need more than four colors to color a flat map so that no two adjacent areas are the same color.





And no, you don't need a fifth color because of the ocean. You could view the ocean as one giant sprawling country and color it blue. Of course under this scenario some land locked countries may also need to be colored blue.





As a practical matter, this is not quite the same question as how many colors are needed to color all countries in the world so that no two neighboring countries are the same color. The reason is because some countries have more than one piece. So that may require an additional color. Also if you don't want to color any countries blue but only water, that would require an additional color.
The answer to this question has been proven to never be more than four, no matter what the countries are like, no matter what map you are trying to color. If you want the oceans to all be blue, that is an additional color, of course.





Wikipedia gives some information on the theorem: http://en.wikipedia.org/wiki/Four_color_鈥?/a>
ooops. i didnt read the question right.