Fabio,
The right ID has already been given by André, Steve & JanJ. Just for the record there really only are two things you need to note in terms of the colour pattern:
1) No white spots on the wing. It should be mentioned that a few Amazon's do have a single or two white spots on the wing, but nothing that can be compared to the more extensive white spotting on the wing of the Green. This feature is useful in both males & females of the two species.
2) No green spotting below the rufous chest. At most a bit of streaking on the flanks. For comparison male Green has extensive green spotting below the rufous chest, not always in the center, but sometimes even forming a band. Again, it should be mentioned that I've actually seen a few male Amazon's that did have a green spot or two in the center below the rufous chest, but nothing that can be compared to what the male Green has.
Finally, whenever you have the luck of seeing a Green Kingfisher, the difference in size will make the ID obvious as it is far smaller than the Amazon (the Green-and-Rufous Kingfisher is a bit larger than the Green, while the American Pygmy is far smaller than all other Kingfisher in this part of the World). Anyway, there are several other features that are useful for separating the Green and the Amazon (i.e. usually more white in tail of Green, many - but not all - populations of Amazon have more distinct white lores, crest usually more distinct in Amazon, bill proportionally larger in Amazon), but the three mentioned above are generally the easiest and all you really need.