At 15:10, the Kenyan team enters the stadium, and along with the native Africans and immigrant descended Indians, you see a surprising number of white men, given that they're less than 1% of the population today.
So, who are they? I understand that colonial officials brought their families along, and occasionally you would get settlers here and there, but the representation here seems awfully high considering this is post independence and they were never big in number to begin with!
Two things to keep in mind here.
Kenya became independent in 1963, so this was the first Olympics the country participated in. To a very significant extent, Africans in the former colony had not been encouraged or supported to train as competitive athletes, particularly not in most of the events that were part of the Summer Olympics in the 1960s, many of which required access to specific facilities or playing fields as well as the relative wealth required to be an amateur athlete in countries that did not have national support structures for athletic training. It was important to most newly independent African nations in the 1960s and 1970s to participate fully in international events and meetings, but in many cases that required trained individuals or resources that they had not had the time to develop only a year or two after independence. So for Kenya to send a team meant inviting just about anyone with a connection to the nation who had even minor facility with the events in question. Only four years later, Kipchoge Keino won two gold medals in Mexico and kicked off a long history of Kenyan excellence in long and medium-distance running.
In 1964, the buy out of the white settler population in Kenya had only just started, so many of them were still in the country. They had dominated public affairs and culture for the previous four decades, and many of them lived in a way that (rather notoriously) mimicked the declining landed aristocracy of the 19th and early 20th C. in Western Europe, including playing posh sports like polo, tennis, lawn bowling and so on. So some of them could plausibly compete in the Olympics (but probably could not have gotten on much more competitive teams in Europe) and were perfectly happy to join the Kenyan team for the fun of it. This not really that unusual in Olympic history overall--many teams have 'ringers' who have some distant claim to residency or citizenship in the country they represent despite being very unrepresentative of the national population of the country they are representing. Moreover, a small but well-known fraction of white settlers had elected to choose Kenyan citizenship and remain in a majority-ruled Kenya, such as the Leakey family and Daphne and David Sheldrick.