Understanding Fiesta greens isn't tricky once you see a few pieces side by side. The Original Green color was called "Light Green". It's shown here in the middle plate. The left plate is the ever elusive Medium Green and the plate on the far right is the other 50's green the Dark Green, sometimes called forest green.
Here is a medium green cup (top left) next to an original light green cup.
Probably the single factor that makes it hard to distinguish Medium green from Light green is that sometimes Light green has a heavy application and can appear almost medium green at times. (I have a tom and jerry coffee mug in light green that I can barely tell from my medium green). Many people refer to Medium Green as "John Deere Green". This seems as good a way to describe it as any. The light green almost looks blue next to it. The forest green is a dark green and there should be no problem distinguishing it
The middle Tom and Jerry mug in the front row is medium green. Forest green is on the right front corner and that's light green in the middle.
Here you'll see medium green in the center with light green at 11 oclock. If all else fails take your bowl out next to the tractor and see if they match.
For what it's worth here is the individual salad bowl in medium green.This piece is only found in Medium Green, Red, Yellow and Turquoise