There is a photo of Hicks and his staff, and they are all wearing the Egyptian uniform bar one. Can't be sure what he is wearing, either a civilian jacket or a British patrol jacket, maybe. That part of the photo is a little indistinct. They are all wearing fezzes (including him) and the others have white Egyptian jackets. Some are wearing matching trousers, some are wearing the winter blue trousers. A studio photo of Baker has him in a fez and a posh high-ranking uniform covered in gold braid and medals. Doesn't look like the kind of thing you'd wear on campaign. The Perry book has an illustration of him at El Teb in an all-white Egyptian uniform, but in place of the fez he has a red, turban-like cloth wrapped around his head.
Edit: There is a contemporary (newspaper or magazine?) illustration of Baker and his staff: two people are dressed as Baker is described above, while several others seem to be wearing British uniforms and sun helmets.
The only uniform info I have on the mounted Gendarmarie is from the same book, the one by Mike Snook and the Perry twins. It is a modern colour illustration, and has them in an all-white uniform with an Arab-style white head-covering (the sort Bedouins are famous for).
Don't have any info on the uniforms of those European mounted police, unfortunately.
As far as I can tell, the two Gendarmarie infantry battalions wore the standard white Egyptian uniform. The troops at El Teb who ressembled zouaves were the men of the Turkish Battalion. They had baggy white trousers, a blue zouave-style jacket, and a red fez. Contemporary illustrations show them dressed as such.
Another way you can relieve the monotony is to add a neck flap coming out from under the fez with greenstuff to some of the troops. I haven't seen any commercial figures like this, but it seems like it was pretty common. The Sudanese troops at El Teb seem to have wrapped their entire heads in white cloth (fez and all). The effect is something like a turban (with just a bit of the red of their fez showing just above their forehead), but the cloth also comes down the sides of their face and under their chin, like somebody with a toothache in old movies and comics. Something to consider to spice up the look a bit.
(Just realised, both those suggestions involve adding more white, the very thing you are trying to get away from - feel free to ignore
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