Spanish Drummers.
Spanish Infantry of the Early Peninsular War, Cronin & Summerfield, p72, states that, from the reign of Carlos III, all drummers had blue coats and red facings, and cites a private communication with Luis Sorando Muzas in 2013 as authority for this statement.
Three sources appear to record these blue coated drummers with the Romana Division in Hamburg in 1807; Augsburger, Suhr and Weber. It might be objected that many of these men wore the 1802 blue uniform and that blue coated drummers were part of the 1802 uniform. Clearly, however, the drummers do not match the 1802 uniform, which was blue with black facings piped red for all regiments. The drummers' uniform, in contrast, had red facings with red and white lace borders.
Persuasively, in my view, blue coated drummers and musicians are depicted alongside the white coated infantry regiments in Hamburg. These white uniforms had to be made in Paris. I can think of no reason why drummers would not have had replacement coats in white had this been the regulation.
The use of this blue uniform for drummers is reminiscent of the Bourbon livery of French drummers in white-coated regiments of the Eighteenth Century. That is how I interpret it.
So, you pays your money and takes your choice, but I have plumped for blue coated drummers faced red, regardless of regiment. I shall also render drummers in the Provincial Militia thus.
Anyway, below is an illustration of the white, faced red, Guadalajara regiment, and the white, faced black, Zamora regiment. Both are Hamburg, 1807.