Jean Restayn states in Fedorowicz's The Battle of Kharkov, Winter 1942-1943 ; "Much of the artwork depicting the Panzer IV's of this period incorrectly show the vehicles with a panzer-grau base. In fact, the Panzer IV G's delivered to the 1. SS-Panzer-Division "Leibstandarte" at the time had a sand yellow base."
Waldemar Trojca also depicts them in this manner, as seen here;
Despite the official start time of February 18th, 1943, for Army Directive HM 1942, Number 181, (the switch from Panzergrau to Dunkelgelb), concerning camouflage at Kharkov, Restayn further states; "...from the summer and fall of 1942 on, practically all new vehicles were delivered to the front in Dunkelgelb." He then continues with a more thorough description of the various colors used during this campaign. Again; "More complex than originally thought."...Please see page 4 Battle of Kharkov for the complete descriptions, as they are too lengthy to list here.
Missing-lynx has had numerous threads over the years concerning this topic, you can search their archives for more info;
http://www.network54.com/Forum/47207/thread/1192676978/dml+panzer+IV+G+box+art+mistake
http://www.network54.com/Forum/47207/thread/1339883226/Colour+of+the+WSS+Panzer+IV+G+on+Kharkov
http://www.network54.com/Forum/47207/thread/1290416004/1290576612/Some+questions+about+Panzer+IV+ausf+G+around+Kharkov+in+early+1943.
http://www.network54.com/Forum/47207/thread/1298513815/Panzer+IV+Ausf.G+Decal+vs+Reality+--+Help!
http://www.network54.com/Forum/110741/thread/1278165088/my+first+hairspary+experiment+-+Pz+IV+ausf+G+Kharkhov
http://www.network54.com/Forum/47207/thread/1173309475/LSSAH+PzIV+F2%27s
http://www.network54.com/Forum/47207/thread/1226008891/1226046460/Color+of+1st-3rd+SS+Panzer+4+Gs+at+Kharkov
In this photo, Dunkelgrau appears to show through the divisional symbol;
I'd best throw in Jentz and Doyle for good measure. Here is their view as the vehicles would have appeared earlier in France during their refit;
Granted, this image depicts an earlier style "F2" globular muzzle brake, but technically still a "G', (see caption on image).
The general consensus on M-L seems to be against the use of red numbers, FWTW. "I think the red number thing started in SS Armour by Stern, which manufacturers [ and other authors / illustrators ] seem compelled to continue with." -Steve Ballantyne.
Colorized photos, difficulty identifying units, disputed tactical number colors, some in gray base coat, some in yellow,...or not.... Tom Cockle and others bring up the possibility of Tropen Scheme being used......it's a whole big can o' worms. Personally, I don't know how much faith I'd put in either Restayn or Trojca, but I throw them out here just to add fuel to the fire...
So.......there you go. Take your pick. You would be hard pressed to pick a messier topic.....