I can understand the disappointment, Rich. Some nice yellow or green-coated dragoons would certainly look good amongst the defenders of Blenheim village.
However...according to the Letrun Histoire et Collections book on Dragoons (Vol1: 1669-1749) the 'Vasse' dragoons were also redcoats, albeit with green facings, breeches and cap (with red bag) and red saddle-cloths.
So it looks most likely that the entire dismounted brigade of dragoons in Blenheim were redcoats.
Incidentally, the above book indicates that the 'Vasse' dragoons only became this when the regiment changed hands in 1706, presumably having been re-built since the 1704 debacle. In 1704 this was the dragoon regiment Heron.