I'm about to make a Sopwith 1 1/2 Strutter for a museum but don't know what color scheme to put on it. There is only one big problem: it has to be of a sqadron that flew in 1917 over Passchendaele (Passendale). The only thing I'm sure of is that it flew there in 1917.

British or French?

The brittish version would be better, but french wouldn't make a problem.

While I do some digging here are a few references.
British Fighter Units 1915-16 by A. Revell, Osprey Pub. Ltd. 1978.
British Fighter Units 1917-18 by A. Revell, Osprey Pub. Ltd. 1978.
Royal Flying Corp in WWI by R. Rimell, Osprey Vintage Warbirds series #1, 1985.
Royal Naval Shipboard Aircraft Developments 1912 to 1931 by Dick Cronin, Air Britain Pub.1991.
Royal Navy Aircraft Serials 1911-1919 by R. Sturtivant & G. Page , Air Britain, 1992.
Sopwith 1 ½ Strutters by J.M. Bruce Profile Pub.
Sopwith Fighters in WWI by J.M.Bruce, Osprey Vintage Warbirds series. #3, 1986.

Here's some fun from a good fellow in GB.

45 Squadron, based at St Marie Cappel in northern France, flew 'strutters' for the first part of the campaign, all over the Ypres Salient including Passchendaele, but later converted to Camels (with a number of their observers moving across the aerodrome to 20 Squadron's Bristol Fighters).

A suitable example might be 'A8296', lost in action near Deulemont 7th June 1917 - if you include the Battle of Messines as a part of (or precursor to) the Passchendaele campaign. The crew were Lt AEJ Dobson and 2/Lt. GAH Davies, both KIA.

Another Strutter lost by 45 Squadron later in the campaign was A1031, 28th July 1917 over Polygon Wood. Lt. GH Walker and 2/Lt. BG Beatty both KIA.
Apparently claimed by Ltn E Hess of Jasta 28. Info on both these a/c from 'The Sky Their Battlefield' by Trevor Henshaw.

Thanks a lot for the information.