Why "Horizon Blue" for the Poilu's Uniform

As all World War I students know, the traditional French uniforms of blue coats and rouge pantaloons made dandy targets for German machine gunners in the opening battles and just had to be replaced.  But why was the horizon blue color scheme selected?

Veterans Visiting the Tomb of France's Unknown Soldier

The evolution of the French uniform is one of the more fascinating aspects of French army history of the period. While several efforts to modernize French uniforms to appear less conspicuous had been undertaken in the decade preceding the outbreak of war, none succeeded in really getting off the ground. It was only in 1912 that progress was made toward developing a new cloth referred to as drap tricolore ("tricolor cloth") and composed of blue, white, and red threads. Approval for the new cloth was already won when it was discovered that the manufacturers of the red dye (the synthetic alarizin) used in the process were all German. Production of the cloth went ahead nonetheless with the red thread simply omitted. The final (heathered) cloth was to be officially composed of three threads — 35% unbleached white, 15% dark blue (indigo), and 50% light blue — with a twill weave.

The cloth itself began production in August 1914 and was officially referred to as bleu clair ("light blue"), per the official decision on 25 November 1914. History has recorded this as bleu horizon ("horizon blue") following a January 1915 issue of the highly popular periodical L'Illustration, which referred to "a new gray-blue greatcoat, called horizon color." Thus, while horizon blue is used as a blanket term for the new cloth, it was never an official term. Furthermore, light blue is technically more accurate when used to describe the cloth generally produced prior to spring 1915 (the captions for images below reflect this terminology). The term "light blue" 'is deceiving, though, as in actuality the range of colors varied from an ashen light blue to a medium blue-gray. While the new cloth did not achieve the true neutral tone original intended, due to the nature of the early dyes, the cloth often faded to a light blue-gray, which melded well with the chalky mud of Champagne and Artois.

Despite the administrative decision-making in the summer of 1914, distribution of the new uniforms had not yet begun when war broke out. . .

Read more at the Website of the 151st Infantry Reenactors. . . http://www.151ril.com/content/gear/uniforms/13