Since every country in Africa was previously colonized at some point, you should be able to find plenty of useful information about any that you choose. I would probably select South Africa, since it is one of the largest and most populated nations on the continent. It was the last nation in which its citizens received equal rights and representation, and the story of Nelson Mandela and the end of apartheid is one of the great stories in modern African politics. It is a country of great beauty and scope with a long history that includes many different different outside influences (particularly British and Dutch).
This really depends on what it is you want to write about and what sort of information you need. You can find a lot of information in the link below to any African country. It will tell you about statistical things like their literacy rate, life expectatancy, things like that. So if that is the sort of thing you are writing about, you can find good information about any country there.
Since you mention colonization, I assume you are doing something having to do with the impact of colonization on countries. If so, I would recommend either of the following countries:
- Nigeria. This is an interesting country to write about because of the way that it was put together by the British without regard for ethnic or religious differences. This has caused a great deal of trouble for Nigeria.
- Zimbabwe. This country only became independent in 1980 and has really hurt itself very badly recently. The black backlash against white farmers is clearly a reaction to colonization, but one which is hurting the country badly.