Clayton
There are varying degrees of the green color on the SOVEREIGN cards. Typically, the cards in the 350-only series appear to have a deeper green back.
The "apple green" (350/460 series subjects) is a distinctive shade of yellow-green, that is un-mistakeable.
The 150 backs can vary in their shades of green.
The 460-only cards usually appear to have a lighter shade of green; however, other 460 backs are a darker shade of green.........
TED Z