Which country has the darkest skin colour in the world?

And also which has the lightest? Not including albinism or melanism or any other pigmentational disorder. I've sort of noticed that when you see black people some are darker than others, some people even have a very rich earthy colour to their skin while with white people they aren't always pale and white some have an olive like complexion and so forth. It isn't for any reason in particular - I'm just interested