Ike,
I think you may want to re-consider the setting for your vignette. I don't think the Stug IV saw any desert action as production didn't start on that vehicle until December '43, after the fighting had ceased in North Africa.
In terms of colors, you have the standard range of options for most German vehicles with a base of dark yellow and your choice of redbrown and/or olive green camo oversprays. You could even go with just dark yellow, if you prefer.