The border of each unit frame healed by Circle of Healing glows briefly. The color of the glow is determined by the number of players/pets healed. The number healed by CoH is also displayed by the mouse cursor. The duration of the indicator can be adjusted from the Custom Options Tab.
red = 1 and 2
yellow = 3 and 4
green = 5 or more
Classic wotlk version can be found in Croutons Priest Pack