Osprey has Bengal Horse Artillery in white* overalls and knee-length boots in the field, no facing colours to paint, by which I mean the collar and cuffs are the same colour as the rest of the uniform. If they're not wearing the overalls then according to the book they would be in laced blue jackets with red collars (it seems when they did wear these some batteries tore off the red collars for some reason). I don't think any of the Mutineer figures are wearing laced jackets, though.
*They call it "white" but it is more like a dusty khaki in the illustration.