My understanding is largely from the Wüstennotstaffel e-book so I'll be paraphrasing from that:
In early 1941 there was no official desert scheme, aircraft would arrive in the typical scheme seen in Europe and painted in the field leading to lots of variety.
April 1941 is when the official scheme came to be, aircraft would be painted in RLM 79 Sandgelb upper, RLM 78 Blau underside, and RLM 80 Olivgrün mottling, prior to being shipped to Africa. Eventually this was done at the manufacturer rather than at a depot in Germany.
The book mentions early schemes of regular RLM 70/71/66 Splinter scheme receiving RLM 79 squiqqles to make it more appropriate for the desert. Later a few Storches painted in RLM 79 upper had squiqqles of the underside RLM 78 to help break up the single colour scheme, Rommel had one like that apparently.
