There is an international protocol in North America for colored leg bands on Peregrine Falcons. The color indicates the origin or subspecies for chicks banded in the nest. The colors in the protocol and their meaning are:
Red Captive bred
Black/red bicolor Eastern United States
Black/green bicolor Eastern United States
Blue Tundra Peregrines
Black/blue bicolor Tundra or Anatum captured off the breeding grounds or subspecies unknown
Green Peale's Peregrines
Black Anatum Peregrines
Characters used on the Peregrine bands are letters and numbers, with one character on the top of the band and one character on the bottom of the band. Older bands may have these characters either vertical or tipped ninety degrees to the left. Newer bands have all vertical characters.
As unique codes for each color are exhausted, the codes are repeated with a 1 mm white line separating them. The color band codes on Peregrines are unique and tied to an individual bird and band number. These bands can be read on a perched bird with the aid of a telescope.
Be sure to report the codes as you saw them (vertical and tipped characters, presence or absence of a white line, band color, code color).