I used a few drops of black food coloring in the marshmellows before I added teh powdered sugar but now its got a purple tint to it. Its resting right now but I can't waste an entire batch when I need to make 1 more batche to cover cake and the cake board for a skateboard halfpipe I have to finish. I don't mind the tint but its really more lavendar than a concrete gray which is what I am looking for. I used Mccormicks black the first time. should I try to add some black Wilton's gel after is sits a bit?

I use AmeriGel's Super Black and haven't had a problem. But letting it rest for a while is wise, as the color will deepen. Good luck!

Of course I don't have any Amerigel colors yet as this is a hobby. Hope the Wiltons gel will work.

If you're starting with white MMF, - color it with 2 or 3 dark colors first (brown, green, blue)...you don't need a lot, just a drop or two.
Once you blend it together, add black to whatever nasty shade you've just created.

THAT black mixed with white (to make gray), won't change color.

I have heard that yellow can off purple since they are two different colors on the color wheel. I would recommend adding just a touch of yellow to see if it will remove the purple tint. I have had tons of issues with the Wilton black either having a purple or green tint. Americolor works better & is pretty similar in pricing.

I had this same problem, I assumed a drop of black would make grey, but I got purple. I googled it, and found the same advice that dchinda just said. It suggested using two opposite colours on the colour wheel, and you'll get grey. So I added some yellow to my already purple'ish fondant, and that worked out well.

I had to add a few drops of yellow to mine after adding black to get grey. But worked great. I used the wilton colors.

Thanks ladies, I did add the yellow. Bit too much but it turned a shade of light brown that I can work with. Its for my nephews birthday cake so the ppurple would not have worked Will get a picture up once I finished it.