From what I've heard (Dana Bell) and read on the internet :
Zinc Chromate = translucent protection product
Zinc Chromate WW2 = yellow pigment added
Interior Green = YZC with black paint added
Dul Dark Green = Interior Green with more black paint added.
Take a bottle of your favorite yellow modeling color, add a little of black and you'll get a perfect Interior Green, *** more black and you'll get a beautiful Dull Dark Green.
Republic Green had a slight blueish hue which may have been due to the black pigment or to insignia blue added (I will check that on my modeling desk). This has to b