In case the links above disappear or for those without a catalog handy, here is the stamp under discussion:
I took a look at about 50 used copies I had to survey their inking accuracy.
As noted above, blue low to tinge the head and back of the right chick:
Yellow ink high partially coloring the bottom of the arc at the base of the adult's leg:
Green high to make lower portion of the chicks mostly green:
Yellow very low to make much of the grass yellow:
Catalog noteworthy? No.