At Forum World War I (Dutch) it is said this Pfalz was overall brown with a white rudder.
At Beeldbank NIMH an rear view can be found of this aircraft. The wings don't seem to have lozenge pattern applied, though some pattern is is visible on the wings.

Scheme Colour name FS-number BS-number Humbrol XtraColor Vallejo Model Color Vallejo Model Air
Standard #1 Wings Lozenge?            
Upper surfaces Bronwn?     160 X619 70.984  
Undersides Light grey            

Check www.paint4models.com for an extensive conversion table with lots of colour and paint systems.

Pfalz DIIIa 1 SMALL
Pfalz D.IIIa: brown fuselage; lozenge on top of the wings.