When it comes to the old school enamel paint jobs this thread on a car form is interesting http://www.thirdgen.org/techboard/body/546612-ultimate-budget-paint-job.html
Where I guy took some Valspar tractor enamel and painted his car ending up with a nice finish for $70. From reading it sounded like he knew what he was doing, did a lot prep work, sanding and polishing etc. I believe Valspar makes the implement paint for JD and CIH though it maybe a blended a little diff. for them I don't know. We all knock the old tractor enamel paint as it needs maintance to keep its shine. I have an old 1978 Case 2090 with original paint. Its white and gets dull and chalky but 10 minutes wih the power buffer every 2-3 years brings the shine back real nice.
Lots of guys still paint tractors with the dealer enamels. Alot of times to insure exact color match. Depends on how much you want to spend I guess. I've also heard of guys using JD green with hardener, let it dry good for a couple months, light sand and clear it with a good quality paint.