No German colonial troops served Germany anywhere outside their own directly immediate colonial sphere. However, some colonial soldiers were recruited by the Allies after they or their colonies surrendered. Thus, much of ex-German Togoland was garrisoned after its surrender by French colonial “gardes indigenes” (a type of tirailleur senegalais) who turned out to be the surrendered ex-German colonial police. Similarly, the 2d King’s African Rifles was dissolved pre-War, leading many of its askaris to join the German Schutztruppe in East Africa. Once a Feldkompagnie surrendered, such askaris often gave up and rejoined the K.A.R. Similar things happened in the Cameroons as the Allies conquered the regions that France had handed over in 1911. Trained askaris were valuable, and both sides would have been eager to recruit them from any source. Patriotism as such did not enter into it (what, after all, should an Ngoni feel for King or Kaiser). Loyalty was to the regiment; once it had surrendered, soldiers might honourably seek their livelihood as they wished. It is possible that some such askaris saw European service for France in regiments de marche de tirailleurs senegalais. British askaris were planning to form an infantry division for Palestine in 1919, but never actually served outside of Africa. I know of no Portuguese or Belgian askaris in Europe, and their forces would in any case have been extremely unlikely to have picked up ex-German recruits (the Belgians fostered a fearsome reputation as cannibals, and Portuguese service was universally despised).
My sources are Marc Michel and Hordern and Gorges (the latter 2 are authors of the British Official Histories of military operations in Togo, Cameroons and East Africa). The Australians also picked up some ex-German police levies in New Guinea.