I am positive that JZ217 was delivered with Sky unders, but like many other escort carrier Avengers (and FM-2's) it seems they were repainted some time in late '44, when they were doing a lot of anti-submarine patrols.
Let me know if you need help with decals for alternative markings. I have what it takes, I think.
This is what 846 Sqn planes were marked like in May '45.
http://en.wikipedia.org/wiki/File:Avenger_...ght_1944-45.jpg
http://www.odin.uk.com/cms/index.php?optio...mid=186#joomimg
Another picture I've never seen before, from '44, showing possibly red letters.
http://en.wikipedia.org/wiki/File:Grumman_Avenger.jpg
Some more nice stuff
http://www.crashsiteorkney.com/page19.htm
Notice that if the underside paint appears to be going in a straight line in front of the wing, without the classic Tarpon "step" after the cowling, and with a "sweeping" style behind the wings and towards the elevators, the aircraft was painted white. Another giveaway is the black antiglare on cowling and front top of wings.