Well a mexican red head and a spectacled are different species.
The specticaled is also called the white fronted and is one of the smallest of the amazons. They have red that goes around their eyes and a white patch at the crown, Yes with this species the males will have that red patch from their shoulder down the edge of their wing.
Mexican red heads, also called green cheeked amazons have no outward sex determination. They are a mid size amazon, similar in a appearance to a lilac crowned and both have a blue/purplish arch going from their eye to near their neck and a red patch on the crown of their head. With Lilac crowns, the purple-blue is more prominant and goes further around the head
Mexican red head
a Lilac crowned
Melanie