Prepare the two packages of green Jell-O according to package directions (with 2 cups boiling water, 2 cups cold water). Divide gelatin liquid into two dishes, leaving one as it is. To the other, whisk in 2 tablespoons sweetened condensed milk to make the liquid opaque. To that one, also add a tiny bit of black gel food color on a toothpick to color the mixture Army green. Start with just a bit, adding more if needed to get desired coloration. Pour the transparent green Jell-O into one 8x8 inch pan, and the opaque Army green mixture into the other 8x8 inch pan.