(Great Value is Wal-Mart's house brand and comes in little squeeze bottles.)
Most food color lines contain a pre-mixed green, but try mixing a few greens yourself. Shades range from Sprout, Seaweed, Duckweed to Pine and Moss.
After the photos are green formulas and hints.
A = Wilton Kelly
B = Wilton Kelly Pastel
C = Wilton Kelly + diluted McCormick Black
Green Formulas D thru M are 1 to 1
D = Wilton Kelly + Blue
E = Wilton Kelly + Royal
F = Wilton Kelly + Hannah Montana Purple
G = Wilton Kelly + Copper
H = Wilton Copper + Teal
I = Wilton Golden + Kelly
J = Wilton Golden + Blue
K = Wilton Golden + Violet
L = Wilton Copper + Black
M = Wilton Lemon + Violet
N = Wilton Juniper
O = Wilton Juniper Pastel
P = McCormick Neon Green
Q = McCormick Neon Green + diluted McCormick Black
R = McCormick Green
S = McCormick 1 part Yellow + 3 parts Blue
T = McCormick 2 parts Yellow + 2 parts Blue
U = McCormick 3 parts Yellow + 1 parts Blue
V = Great Value 1 part Red + 3 parts Green
W = Great Value 3 parts Yellow + 1 part Green
X = Great Value 2 parts Blue + 2 parts Green
Y = Great Value 3 parts Yellow + 1 parts Blue
Z = Great Value 3 parts Blue + 1 parts Green
a = Great Value 2 parts Yellow + 2 part Green
b = Kool-Aid Lemon-Lime
c = Kool-Aid Lemon-Lime Pastel
d = Kool-Aid 1 part Lemon-Lime + 3 parts Berry Blue
e = Kool-Aid 1 part Lemon-Lime + 3 parts Pink Lemonade
f = Kool-Aid 3 part Lemon-Lime + 1 part Black Cherry
g = Kool-Aid 3 parts Lemon-Lime + 1 part Grape
h = Kool-Aid 2 parts Lemon-Lime + 2 parts Ice Blue Raspberry Lemonade
i = Kool-Aid 3 parts Lemon-Lime + 1 part Orange
j = Kool-Aid 2 parts Lemon-Lime + 2 parts Orange
k = Kool-Aid 1 part Lemon-Lime + 3 parts Orange
l = Kool-Aid 1 T. Berry Blue mix + 4 drops McCormick Yellow
m = Kool-Aid 1 T. Berry Blue mix + 1 drop McCormick Yellow
n = Easter Unlimited Easter Egg Dye Green
Green formulas o thru 2 are 1 to 1
o = Easter Unlimited Easter Egg Dye Yellow + Green
p = Easter Unlimited Easter Egg Dye Blue + Green
q = Dudley Easter Egg Dye Teal + Green
r = Dudley Easter Egg Dye Yellow + Green
s = Dudley Easter Egg Dye Blue + Green
t = Dudley Easter Egg Dye Purple + Green
u = Dudley Easter Egg Dye Brown + Blue
v = Dudley Easter Egg Dye Pink + Teal
w = Dudley Easter Egg Dye Purple + Teal
x = PAAS Classic Egg Kit Orange + Blue
y = PAAS Classic Egg Kit Blue + Teal
z = PAAS Classic Egg Kit Purple + Spring Green
1 = PAAS Classic Egg Kit Teal + Spring Green
2 = PAAS Classic Egg Kit Yellow + Blue
3 = McCormick 1 part Yellow + 3 parts Green
Green can sometimes be finicky, if there is a large amount of blue in the mix.
A trick is to add your vinegar and heat to 180 F degrees and allow to cool to room temperature. If some blue remains in the dyebath (and you'd like more to bond to the wool), reheat to 180 F and add a bit more vinegar. Allow to cool again.
Sometimes, especially with the Wilton Blue and Royal and large amounts of the McCormick primary Blue, it will never bond completely.
The McCormick Neon Blue and Wilton Sky are less of a problem.
Here is a page on making green yarn in other ways.
Having trouble making your blue food color behave? Hints and photos of which food colors are really in Wilton blues.