Honestly Tom in North Africa anything could have been possible. I've read where captured Allied colors were sometimes used, Italian colors used on various things, etc.
The Luftwaffe used RLM colors and the Afrika Corps would have likely used RAL colors. By this time the German industry was turning out vehicles painted from the factories in RAL colors.
But it's a sticky subject for sure. One that I don't claim to be an expert on. I only know what I have read from various books and online articles over the years. One good set of books I have is the three part collection called "Panzer Colors" and it has a complete section for just the Afrika Corps.
Believe it or not, quite often they simply used mud as a camouflage color. They would mix some up and smear it on the vehicles. Once it dried they had a perfectly matched color for the surrounding terrain.
Thanks again Tom for your input.
You are right on the money with your statements.
Here's a picture showing the Testors / Model Master color chart along with the corresponding paint numbers.
Plus if you add in the sun fading effects on the paint and how the effects of accumulated dust / sand from the desert and how this will change the looks of a color, then I would simply say go with what you want to. As long as it looks correct to the builder, it's probably "close enough ".
Take care Tom, and Merry Christmas to you.