It’s been a long time since I used mine, but from memory the drum has to revolve around the shaft. The pawl inside it is operated by the lever at the back of the machine- in one position the wheel is free to rotate (when in work) and in the other position the pawl moves out to contact a stop which locks the drum to the wheel, in effect making the rotation of the wheel do the work of lifting the frame out of the ground. This is why only the left hand wheel has strakes cast across the tread so that it can grip enough to drive the lifting mechanism. The right hand wheel only has a ridge cast into the tread in line with the direction of travel.

There wasn’t an exact shade that the factory used; it was difficult to buy any paint at the time unless it was the same shade used by a major user (such as Army, Royal Navy, etc.).
The shades of green that were used seemed to vary from Mid-Brunswick Green through to Dark Brunswick Green, and the wheels on the implement were painted in the same shade of green to match.
Keep persevering with it- it means another one saved.