I vote for one nation = one colour, even for cavalry and artillery which clearly didn't wear this colour. Some of us just don't have time to paint hundreds of figs, so uniform national colours is a great idea.
Please reread my previous mail. The fact is that although different nations were enemies they often fielded men uniformed in the same colour. For 18th century Europe Britain, France, Spain and most of the German states fielded artillery dressed in dark blue with red facings. Only the woodwork of the artillery pieces were different colours. If you want all arms of each nation in 1 uniform colour then play Risk and leave the serious historical miniature enthusiasts to enjoy a true mix of colours in each army. Also give painting a try I for one hate green, red, blue etc horses.
I was born in 1961 so remember well the Airfix sets. I remember hat their Napoleonic French Imperial Guard were an instnat favourite of mine partly because they were made in grey. Their other excellent set were the Prussian Landwerh produced in a Prussian blue. It is such a shame that these two sets were made underscale.