My X 720 is a tad low on coolant and I don't know what type to add to it. The stuff in the overflow tank is green, and the manual says use JD Cool Guard. I have searched compatibility tables and it seems that the JD coolant color is Amber. I should note that the machine is a 2007 model that I bought used last year. Does my machine have the wrong coolant in it? Is there a brand that is compatible to Cool Guard, or can I use any green antifreeze if green is OK?