Sorry mate,

there are no distinguishing features / tribal distinctions on any of the uniforms that would lead one to a distinct Regiment.
All I can confirm is that they are wearing KDs, with puttees (or hose!), and Wolseley (pith) helmets. I can discern no medal ribbons, badges or shoulder titles - We can't even see if there is a flash on the side of the Wolseley!!
All that is different, are the diamonds on the corporal's chevrons on the chap seated to the left...