One of the Dutch horse regiments sent to Ireland, I took the uniform details from Grant's "Armies of Marlborough's Wars, vol 1" (grey/ white coat, lining and cuffs is all he lists, however) and used a large (read "enormous") dose of guessing and creativity for the flag.
The regiment's CO is listed in Sapherson's "William III At War" as Armand Nompar de Caumont de la Force, Marquis de Montpuillan. He also states the unit was raised in 1672.
I took this to mean the unit was Huguenot French (!). I also checked where Montpuillan was and found it to be in the Lot-et-Garonne region of Aquitaine in SW France. Thus, I came up with a white flag, white cross, added a fleur-de-lys in each canton and the arms of Aquitaine in escutcheon to finish it off.
Now watch someone come up with the real thing!!!
Figures are Wargames Factory plastics. Not the greatest figures, but well priced and great entry level to this period.
Gary