In the London Review of Books, T.J. Clarke reviews Revolution: Russian Art 1917-32, an art show put on by the Royal Academy in London. His review is illustrated, among other images, with this photograph, captioned “The Red Army with the black square.” It gets at least one of the colors wrong.
This cannot be the Red Army: the servicemen in the foreground are pictured wearing shoulder boards. Their absence was a distinguishing feature of Red Army uniforms during the Civil War. Old-style shoulder marks were anathema to the Reds in the early years after the revolution. It was only in 1943 that shoulder boards were re-introduced, so that at the end of WWII Soviet army uniforms resembled the imperial army of 1916 more than the Red Army of 1920.
In addition, everyone in this photograph seems to be wearing peaked caps, and soldiers in the background have rolled-up greatcoats over their shoulders. Both would be typical of the Russian army during WWI, prior to October 1917, but not of the Red Army in the Civil War years.
A Google image search reveals that the photograph shows servicemen of the 39th Tomsk infantry regiment and the scene depicted is a political meeting in 1917 – apparently in summer, between the February and October revolutions. The officers in the foreground seem to be skeptical of the men with revolutionary slogans and the black – or red? – square. With good reason, considering the likelihood of being killed in the next 5 years for a commissioned officer in this army.
Curiously, the regiment’s “chef” – which probably means “patron” or “honorary colonel-in-chief” – was the Austrian archduke Ludwig Viktor, from 1873 until, I imagine, the start of WWI. Wikipedia’s English entry on this gentleman, nicknamed Luzi-Wuzi, uses amusing archaisms such as “homophile soirées” and “transvestitism.” James Conway at Strange Flowers has written about Ludwig Viktor’s (mis)adventures here and here.