French Artillery Carriages
At the beginning of the XVIIIth century, gun carriages were probably red as were the gun carriages of the French Marine Royale. However, by the time of the Seven Years' War, gun carriages of the French army were blue to distinguish them from the equipment of the supply train (caissons and carts), painted brick red. Furthermore, canvas used with artillery equipment were usually decorated with a device consisting of two crossed cannon (in saltire) with a crowned "A" or "AA". The change to blue occurred very soon after the Vallière reform of 1732, even though the precise date is unknown.
Nevertheless, most modern books continue to mention that the French gun carriages were red during the Seven Years' War, associating red to the Vallière system of 1732 and blue to the Gribeauval system introduced in 1765. This is probably a misinterpretation of the following facts: after the Seven Years' War, an argument arose between the "reds" proponents of the Vallière system and the "blues" supporters of the Gribeauval system. However, this had nothing to do with the colour of the gun carriages but rather referred to the colour of the artillerymen's waistcoats who changed in 1765 and would become a sign differentiating each of the two opposed generations.
Moltzheim and Blarenberghe, the latter being considered as a very reliable source, illustrate blue carriages.
Indeed, Louis-Nicolas van Blarenberghe was commissioned from 1779 to 1790 by king Louis XVI to realise paintings of the French operations during the War of the Austrian Succession. As early as 1748, Blarenberghe had been the official painter attached to King Louis XV. As could be expected, even if he painted his series on the War of the Austrian Succession at a later date, the cuts of the uniforms are very precise and depict exactly the uniforms of worn during this war. Similarly, these very precise paintings all depict blue gun carriages of the Vallière system. For examples, see:
Moltzheim also illustrates blue gun carriages in his paintings depicting the French artillery in 1745, 1757 and 1760. However, his work is not as reliable as Blarenberghe's. For example, he depicts pieces who do not belong to the models in use from 1732.
Moltzheim might have mistakenly represented artillery piece of a later period (around 1776) but it is almost impossible that Blarenberghe had made the same mistake. As mentioned before, he clearly depicted gun carriages of the Vallière system and uniforms of the War of the Austrian Succession. Therefore, we believe that blue gun carriages were in use in the French army as early as 1741.
Jean-Louis Vial of Nec Pluribus Impar for the initial version of this article.