They did have the A-6 alongside F and G-models. See here
http://www.ghostbombers.com/SG4/sg4frame.html
I can't say for certain that the A-6 aircraft had the green/brown camouflage but all the pictures of SG 4 aircraft in Italy (mostly Fw 190 F) that I have seen show such camouflage.
Some of those photos can be found in these books:
Nick Beale, Ferdinando D’Amico and Gabriele Valentini,
Air War Italy 1944–45, the Axis Air Forces from the Liberation of Rome to the Surrender (Airlife Publishing Ltd., Shrewsbury, 1996) ISBN 1 85310 252 0
J. Richard Smith, Chris Goss, Martin Pegg, Andrew Arthy, Nick Beale & Robert Forsyth,
Schlachtflieger: Luftwaffe Ground-Attack Units 1937–1945 (Midland Publishing, Hinckley, July 2007) ISBN-10: 1857802748 and ISBN-13: 978-1857802740