The standard colour of the British army uniform changed with the Boer War (1900) to khaki, because wearing red coats made easy targets. Before that, only the Royal Artillery and certain troops who had taken inspiration from the Central European hussars wore blue.

Captain Sterne's uniform would be the one I'd expect, the later blue uniforms in the pictures are post 1900. The Sergeant from the Army Hospital Corps reminds me of the 'day uniform' of the Chelsea Pensioners (for more information, https://www.chelsea-pensioners.co.uk/)

The Russian Holmes uniform looks to me more continental Europe.