I've only been able to find two references to Walloon infantry in my limited resources on the War of the Spanish Succession. Charles Stewart Grant in his book, "From Pike to Shot – 1685 to 1720," gives the following for seven regiments of Walloons in Austrian service:
dark green coat; crimson cuffs, waistcoat, and breeches; white stockings
Pat Condray in his pamphlet, "A Wargamer's Introduction to the Age of Marlborough," says the German, Walloon, and Swiss foreign regiments wore blue coats of various shades. Here are some of the specifics for some regiments, but I don't know which ones might be Walloon:
Zurlauben: medium blue coat; red cuffs; red vest; red trousers; grey stockings
De Lenck: medium blue coats; red cuffs; blue vests; red trousers; blue stockings
Alsac: "Turkish" blue coats; scarlet cuffs; scarlet vests; white trousers; grey stockings
Reding: dark blue coats; red cuffs; red vests; blue trousers; white stockings
Greder: ? blue coats; red cuffs; medium blue vests; dark blue trousers; dark blue stockings
France occupied most of the area containing the Walloons during the War of the League of Augsburg. I haven't seen any references in my limited resources to Walloon units that weren't in someone else's army during the War of Spanish Succession.