Thanks again very much. I'm beginning to feel slightly embarrassed by taking up so much of your time.
It's indeed a very interesting litho but as always a bit vague on details. One of the figures in the foreground (probably wearing a coatee) has cuffs that look more like a French Fusiliers' than anything I've ever seen on a British or HEIC uniform. The seated one on the left also has a cuff with two parallel buttons, not something you expect to see on a sepoy.
Those in the back ( I'm assuming the two on the right are supposed to be officers) seem to be wearing red shell jackets but with contrasting cuffs and collars. Can't see any white loops on their chests as they are turned away from the viewer, and no coat tails, so I'm assuming he was portraying shell jackets.
Buy yes, that white summer dress is very interesting. Would make a nice change from the normal coatee and/or the off- white mutineer clothes. I too think that the wings wouldn't be worn on a shell jacket, same as the fringed epaulettes weren't worn by the centre companies. At least not in the field. But of course you never know how much 'peacock element' a particular regiment has, and they might be just showing of at the range.
All in all an interesting and very nice print, but as you suggested not something I'd use as a hard reference.