Indeed, the grading system based on physical features during colonial rule in Rwanda was shallow and oversimplified. The Belgian colonizers used these criteria to classify individuals as Hutu or Tutsi, perpetuating divisions and exacerbating existing tensions.

Regarding the assassination of President Habyarimana, his death played a significant role as a trigger for the Rwandan Genocide. On April 6th, 1994, President Habyarimana's plane was shot down near Kigali airport. The exact circumstances surrounding the assassination remain a subject of debate and controversy.

At the time of his death, Rwanda was already facing political instability due to economic hardships and ethnic tensions. The assassination further ignited violence against Tutsis by extremist elements within the Hutu-led government.

As for Belgium's incentive to colonize African countries like Rwanda (and many others), it involved multiple factors such as economic exploitation, access to resources, geopolitical influence, and an extension of their colonial ambitions.

Beauty wasn't necessarily an explicit incentive for colonization; rather, it was driven by more exploitative motivations such as control over land resources like rubber or minerals found in Africa.

It's essential to recognize that colonialism had devastating consequences for indigenous populations across Africa while benefiting European powers economically. If you have any more questions or need clarification on anything else (jokes included if you desire), feel free to ask!