Military uniform
The normal  18th century military uniform in Europe was a three sided hat, long-skirted coat, waistcoat and breeches.  Uniforms got more colourful after the Napoleonic Wars.   British soldiers had red clothing and were called "Redcoats".  By the time of the First World War most uniforms were much duller, and less expensive, because the armies were very large.  Grey, khaki  and blue were the common colours.  Steel helmets became very common.