This is a very common problem. If you google this issue, you will see the same question over & over again. Here is an answer that I found interesting on another cake site: This is common.
“I learned in art class that when you mix all 3 primary colors, you get black….red, blue, yellow.
In the 70’s, when they took the #2 Red Dye off the market, our stable red disappeared and there was not a good replacement. We’ve been dealing with the issue ever since.
When the red fades away, all that is left is the blue and yellow …. which equals green.
I buy black icing from my cake supply store, and even when it’s new, I can see the green tint along the edge.
we just don’t have a stable red and haven’t had one for over 30 years."
If you add a tiny bit of the opposite color on the color wheel, it will neutralize the green. In this case, it would be red so I think the information is correct.
