The map above simply shows the shade of red that appears on each country’s flag, assuming of course it has red on it. The data comes from here, which shows that 148 out of 192 countries (77%) have some red in their flags.
The reddest flags are:
The map above shows all countries whose capital was not their largest city, based on population, in 2010. This explains why South Sudan does not appear as a separate country, however if it did it would not be among the countries included (Juba is both the capital and largest city of South Sudan).
Here are a few of the more interesting facts about these countries and cities: