This should help you:
"Buffons Macaws are different. They can be separated visually from the Military Macaw by size, plumage color, and the color of the eye. They are large, certainly among the largest of the macaws. Even the subspecies, the Guayaquilensis, is significantly larger than the similar looking Military. The Ambigua averages 2# 12 oz., (19 individuals weights), males being 6 ounces heavier on average than the females. The Guayaquilensis averages 2# 4 oz., (4 individuals weights), males being 3 ounces heavier on average than the females. Militaries average 1#15 oz., (22 individuals weights), with no consistent difference between them. These are statistical averages, and by no means a maximum or a minimum for any individual bird.
Buffons are a different shade of green than the Military, being more chartreuse than a dark green. I have also seen signature feathers (small out of place colored feathers )on Buffons, sometimes red, yellow or orange, on a bend of the wing or the head. I have yet to see signature feathers on a Military. Photographs of these birds can confuse you; different films, lighting, and developing techniques show all sorts of different shades of color. I have one snapshot of a Buffons that shows a more yellow tone--but it is just ink! People who know birds are really excited about that until I tell them it is really a green bird, and not a yellow mutation.
The Buffons tail feathers are longer, reflecting the overall greater size of the bird, and varying shades of red and orange. Most tail feathers have the vibrant burnt orange, but can shade to a burnt ember color, depending again on the individual bird. The Military's tail tends to keep to the darker, red umber coloring, and a much smaller size.
There is a difference in the eye color which Barbara and I discovered some years ago. The correct eye color is not currently reflected in the hard cover "dictionaries" of parrots. In the Buffon macaw., there is the black pupil, surrounded by a wide, plain steel grey ring, then a fine black line, and one soft yellow band around that. In the Military, there is the pupil, and three orbits of yellow color surround that. These color bands are somewhat diffused into each other. Once you have seen it in person, you will not mistake it. The Guayaquilensis that we have seen also have the distinct grey ring, like the Ambigua."
