Some good suggestions in those links there. Unfortunately the Great War leaves even less for your Seebatallion to do than the earlier period. They served in China and on the Western Front (in different uniforms of course - bloody typical!), but weren't involved in the African campaign.
but maybe there are some alternatives instead of trowing away your seebataillon minis...in WW1 in East Africa they were some
Schutzencompagnies and some
Reservecompagnies totally formed by "whites only" soldiers..one of them was composed mainly from hastely recruited foreign colons living in German East Africa (Boers, Swedish even Italians), a sort of German Foreign Legion that also fought succesfully at Tanga...in an almost unknown book/memory telling the story of an Italian family living in German East Africa (Trent'anni d'Africa by Mongardi) whose author together with his brother fought with one of those companies (yes in 1914 Italy was neutral or, at worst, allied with Germany and in any case the 2 Mongardi brothers where tought and convinced fraudolently by Von Lettow in Person that Italy had just declared war to the Allies)..according to the author their uniform was kaki with "a beautiful cork/pith helmet that unfortunatly had to be spoiled by making holes for the insertion of camouflage branches as ordered by the German officer"....so you can use your seebataillon kaki clad germans with pith helmet, maybe with a few types in slouch hat, as a convincing proxy for a foreign Schutz Cp even in WW1 East Africa...don't forget that a few selected types could be used also in Kamerun.to represent white reservists..