"The answer on the paint is "Both ways are right". It all depends on the time period.
Early in the African campaign they would have been Desert Yellow over Panzer Gray. Keep in mind that the German's at this stage did not have enough Desert Yellow paint so there is a lot of variation and most vehicles would not be completely covered. The interiors and other similar areas would have been left in Panzer Gray. Add to this it was common practice to cover the vehicles with mud instead of paint. This lasted for a short time and produced some interesting weathering patterns.
If the vehicle was later in the campaign (like in Tunisia), then the vehicle was either received in Desert Yellow or Dunkel Gleb overall (applied at the factory), or Panzer Gray (and then sprayed with Desert Yellow).
No matter what you choose. Have fun with it. I've just finished building a 223 and it is ready for paint. Mine is going to Russia!"
That leaves me with a second question, what do I need to give the effect of the tires being covered with sand and the bottom of the vehicle being weathered like it's been in use for a bit.
"Hey there,
Why don't you join in the Small AFV group build! We were just talking about the exact topic, as myself and a couple of others are doing or thinking of doing 223's. I know there is detail sets, but I don't know specifics."
Thanks for the info, I'll definitely join, hopefully I can finish on time, schools got me really busy, but I'll try to finish