If you are trying to use up old icing then I would mix the two colors to together and then add cocoa powder until it is brown.I don't think there are specific colors that will create brown, you probably would just end up with a really yucky mess.
Deborah
How do you get the color of frosting to be really rich and dark brown? I've seen so many pictures of beautiful cakes with really dark brown frosting, but when I use cocoa powder in my frosting recipes, it comes out medium brown, not almost black like some pictures I've seen on this site. Please help!
I know some people use hersheys syrup instead of cocoa powder but I am far from being an expert, so hopefully someone else can help you.
Deborah
I had this problem last week when I was doing a chocolate butter cream wedding cake. I ended up finding the new Hersheys Special Dark Cocoa powder. It worked perfectly...here is the link to my post...
http://www.cakecentral.com/cake-decorating-ftopict-490303-.html
HTH!
I've also used regular cocoa powder and then added some brown coloring to the mix to darken it.
Valerie
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