Pre-WWII painting scheme (the one on the left) came from an unusual place. One of the stacks of the old coal gas plant in Ankara, Turkey... My grandies had lived around. When I had asked grandpa about the "funny" painting of the stack, he told me that it had been form the days of the WWII. This was 60s BTW. I could not find any color image of the T-6 but the stack, taken before it was demolished. The colors are based upon that picture of the stack.
The one on the right is in standard khaki as the old camouflage patterns had been dropped as Turkey's journey into NATO was about to commence.
BTW, many thanks to the other contributors of this forum. I feel like I am at a military museum that has no exit!