Looking at Kronoskaf.com, Russian artillerymen wore red coats, waistcoats and breeches. Artillery carriages were also red with black fittings.
This will be a challenge. From photos of artillery displayed at various museums in Russia, the carriages were actually stained giving a chestnut appearance.
Uniforms, if one reads between the parentheses were nearly orange and not a true red. This should offer enough margin to create some contrast so they don't look like Santa's helpers.
General officers wore similar uniforms as the infantry, but edged with gold lace. The staff can be dressed in uniforms of their particular regiment, so these adjutants will come from Cuirassier and Horse Grenadier regiments.