Fun fact: The red uniform trousers had been introduced to support the French dye industry.
When the Minister of War Adolphe Messimy proposed to switch to a more drab uniform in early 1914, this was rejected after opposition in the press that it was “contrary to French taste”.
In December 1914 it was finally changed. Not because of the high casualties, but because they had since replaced the natural rose madder dye with German-produced artificial alizarin, which they now couldn’t get anymore.

Hugo Boss looking over the trench line in 1914 and taking notes.

It really was a glorious uniform, though.