Originally Posted by Rocket Doctor

I inquired with two very reliable sources and here is what the answer is to the green motors.

The casing supplier ran out of paper and couldn't get any in time to meet the Estes demands. They did have stock of blue and green paper that had been used for the engine shipping tubes ( I believe that was the Northeatern Paper Tube Company?), so, in order to keep up with customer demands, that was what was used for the engine casings. Same material, but colored.