After 35+ years, the difference between green and red is about like front distributor vs side distributor on a Ford. You can find parts for either, you just need to be specific when describing it.
But trade your Ford for it? This is a big step down in weight and pulling power. I have a YM186D that is approximately equal to the 1500D in capability. These are both good
small tractors.
Maneuverable, yes, but I feel like I'm always struggling for traction discing or pulling my watering trailer on soft ground. The Ford would handle these tasks as if there were nothing attached on back. If the Ford is too big and clumsy for your application this is a good trade (assuming equal condition). And the Yanmar will run for years without the fiddling a gas engine requires - probably a welcome improvement for you. But be sure this small tractor is suitable for your intended use.