I agree, it might be hard to match if the other paint is faded.
But, what you want, color-wise, is the newer, brighter green that JD offers. It's called "Agricultural/Commercial & Consumer Equipment", not to be confused with the earlier "Classic" green.
The JD part no. is "TY25624 -- Ag/C&CE Green" for the 12 oz rattle can.
Rustoleum offers a line of paint called "Specialty Farm Equipment", with an exact color match. The part no. for their 12 oz rattle can is "7435830 -- John Deere Green."
I have bene using both recently, and have found the Rustoleum is preferable in a number of ways. But I don't have a spray booth. Also, I've read where some say the Rustoleum is tougher/more durable, but the JD paint better resists fading due to UV exposure. Time will tell, I guess.