They aren't free (unless your college has institutional access), but they are available from British Online Archives in the collection titled Colonial Africa in Official Statistics, 1821-1953.
A single-user license currently costs £20 for 1 week, or £40 for 1 month.
Depending upon your exact needs, other reports published by the UK Colonial Office may also be of interest. For example the UK Colonial Office also published short annual reports for each of the the UK's African colonies, which contain useful background information and some (limited) statistical data.
The Internet Archive appears to have a number of these reports, including the Annual Reports on Basutoland from 1931 to 1963 (with a break in the series from 1939 to 1945), on Gold Coast (modern Ghana) from 1946 to 1954, and on Kenya from 1932 to 1962 (also with a break in the series from 1939 to 1945, and the report from 1955 appears to be missing). I've linked to examples of these reports below:
The 1931 Annual report on the social and economic progress of the people of Basutoland
The 1946 Colonial Annual Report on the Gold Coast
The 1932 Annual report on the social and economic progress of the people of the Kenya Colony and Protectorate
For other reports in this series on Internet Archive, you can try searching with the name of the colony or protectorate together with the word 'report', where the creator is 'Great Britain. Colonial Office', or simply browse the (currently 534) items where 'Great Britain. Colonial Office' is listed as the Creator.