Nice customs, all!
Choosing uniform colors for countries in the 18th century is a difficult task, as they weren't exactly standardized. One is pretty safe with red for the British and white/light grey is a good choice for France, prior to Napoleon, although certain regiments wore blue. For Spain, white/light grey and were common, although blue and I think red existed too. The problem is that different regiments had different colors so a nation's uniform wasn't standardized like it was from the mid 19th century on.