Sky Blue
Humbrol Authentic Colour MC9
Humbrol Authentic Colour MC9 »Sky Blue«, a muted light blue hue included in the Napoleonic French and Prussian paint set, compared to Revell 361.50 »Light Blue« and our own mixture of »Sky Blue«, using six parts Liquitex 170 »Cobalt Blue«, three parts PRIMAcryl 13.101 »Titanium White«, two parts PRIMAcryl 13.789 »Neutral Grey«, and one part PRIMAcryl 13.210 »Vanadium Yellow deep« – See our tutorial How to Mix Historic Colours: Humbrol Authentic Colour MC9 »Sky Blue«.
Humbrol MC12 »Prussian Dragoon Blue« ist darker than MC9 »Sky Blue«, the latter seems to have been intended as a facing colour of certain 18th and 19th century regiments. Most importantly, MC9 »Sky Blue« is considered to be the best match for the sky blue trousers worn by Union and Confederate troops of the American Civil war.
Since Humbrol Authentic Colour MC9 »Sky Blue« is no longer available, and Humbrol does not seem to have included this colour in its current range of acrylic paints, mixing your own »Sky Blue« is the way to go.