SPQR7070,
You probably already know the 2 cavalry units present with General Burrows brigade at Maiwand were 3rd Bombay Light Cavalry and 3rd Scinde Horse. Luckily enough our fellow LAFer Neil from "Dining Room Battles" posted some great pics of his own 3rd Bombay Light Cavalry just a few days ago, here:
https://leadadventureforum.com/index.php?topic=135764.0Back in 2010 I did a deep dive searching for visual and/or written information on uniforms of both units while preparing troops for my 130th Anniversary Maiwand game. Unfortunately I didn't find very much.
W.Y. Carman first volume on Indian Army cavalry uniforms has some information.
He describes Third Bombay Light Cavalry having dark green kurtas (Indian cavalry trooper blouses), and turbans with red kullahs, dark blue lungis with red and white stripes. It also mentions that the cummerbund/waist sash was made from matching material, rather than just a solid color, which is an interesting detail but might be a bit of a challenge for 28mm or smaller figures. Carman has no info re: field uniforms for the Second Afghan War, which probably were khaki kurtas (Indian cavalry blouse) and blue or khaki pants, but if you want to you could use the green kurtas, and make them more colorful and singular.
Illustration of a Sowar/Trooper of 3rd Bombay Light Cavalry, 1890 by Chater Paul Chater:

3rd Bombay Light Cavalry on parade:

RE: 3rd Scinde Horse, there is a note in Carman that c.1879 British officers wore a pugri on their spiked helmets which resemble typical foreign service helmets. A picture from 1888 shows a Naik (corporal) in khaki kurta with yellow rank chevrons edged red and a “red turban striped yellow and a dark color” – which as you will see in the similar picture below could be dark green or dark blue or maybe even black; the same Naik has lighter khaki breeches and dark blue puttees (pretty typical for Indian cavalry of the era) and brown leather ankle boots. The regt. did wear dark green dress uniforms, so maybe that’s the “dark color” in the 1888 turban. In 1901 the 3rd Scinde Horse dress regulations mention a “change to a blue kurta” so I think this reinforces the idea that they wore green previously, or of course khaki in the field.
Illustration labelled "Scinde Horse" (2nd and 3rd Scinde Horse both served in the Second Afghan War):

Not 100% certain of the validity of the label on this photo, but it says, “Officers of the Scinde Horse.” It isn't dated but my guess it's probably from either Queen Victoria's Jubilee in 1887 or her Diamond Jubilee of 1897:
