Hi The Turks didn't have much time to repaint most of the German war material, however, the captured Serbian guns (French made 75 mm) would have retained their original colour. A Grey-Green is good colour for applying to the artillery piece.The Germans provided both German made 75 mm and 77 mm guns. Notwithstanding larger calibre and the Austrians with their contributions in war material to the Turks.
I do have some in the sandy-brown colour. By the way the Aussies captured Italian made70 mm Model 1902 mountain guns from the Turks at Magdhaba 23 Dec 1916. Checkout Askaris miniatures. Also look at the Krupp mountain gun from the same company.
The Battle-Honours artillery piece is a nice gun, but be careful of the sight as it is brittle and can easly break without too much effort.
A good book if you are interested "War Trophies" From the First world War 1914-1918 by Major RS Billett.
God Bless
Helen