Thanks to everyone,
Here's what I've learned so far, both from hear and from the chaps over at The Bengal Club who have been emailing me images.
1.) Foundry Zanzibaris are a good place to start... For the 'Not Naked' figures. However, if the photos are accurate for running about the countryside, instead of just posing for photos in town, then there seems to be more cloth involved. It's a much 'bulkier' garment. Most of the time the headgear, which is sometimes a low fez and sometimes a turban thing, also appears to be white.
2.) Colors appear rarely, and in light pastels, but only in water colors created by Frenchmen.
3.) One has the impression that in 28mm you might get away with Tuaregs, but with their faces exposed. So I guess some sort of a head swap.
4.) Unarmored/unpadded cavalry look a lot like Tuaregs, with that big shield.
5.) I actually have a couple of packs of the Perry Bros. Mahdist heavy, padded, cavalry, but was hoping to paint that up for East African heavies.
More to come later... I hope,
MW