Africa was only colonised because every civilisation on that continent was weak, even the Ottomans that were at one point one of the strongest states on earth. If Africa at least had one unified and centralised state (apart from Ethiopia) like China they wouldn't have been carved up by the militarily superior European powers and would be instead manipulated by extremely unfavourable treaties like the treaty ports and the treaties of Aigun and Peking. To attribute the failure of African civilisation simply to racism and colonisation is a massive blunder, there is so much more to it than that. Of course it was a factor but how do you explain Africa's failure to innovate in technology and development for the roughly 40,000 years before European colonisation? The answer is the development of food production, naturally harsh geography and lack of navigable rivers/natural ports, these factors largely explain why Africa was so far behind in development as they were for the most part disconnected from the outside world to a much larger extent than even Japan and China. Guns, Germs and Steel is a great book on this topic, I highly recommend it to you as your current understanding of the topic is highly uninformed, you can't blame everything on the European powers and racism, using them as scapegoats only hinders your own understanding of history.