In the ship visiting a colonial port, their first objective will be to go raiding, a la the last cruise of SMS Emden OTL. Koenigsberg, Emden, and an American cruiser will terrorize the IO. The number of ships sunk or taken will send maritime insurance rates skyrocketing, ships will be held in port for lack of escorts, and RN, French, and Japanese warships will be diverted from other missions to hunt the raiders. When they do make port, they'll be bottled up pretty fast, and have a choice: a death-or-glory ride, or scuttle. They scuttle (or in Emden's case, get caught and shot to pieces), and thus the crews go ashore to fight with the German Colonial Force.
How about a German-built gunboat on one of the African lakes, but with an American crew? U.S. Navy sailors man one of these gunboats, and it flies the Stars and Stripes.
The ultimate irony would be in GW II, where it happens again. And a couple of the Chief Petty Officers on this newer cruiser were seamen the first time around, and like last time, they fight their war in Africa....