I tried the trick -- coloring the BC pink (used Wilton's Pink) first then color it with red (used Wilton's No Taste Red) -- didnt work. Tried adding some of the Wilton Red Ready to Use in a tube -- with no luck. Anyone out there that has done it with success????? Do you remember the amounts? Was disappointed as I needed a true red bc but had to settle with pink. 
If you can go with the Americolor brand for such deep colors like red and black. If you must use Wilton's then you are just going to need lots and lots of the red. I would use the no taste red, otherwise the flavor isn't very pleasant! Also, if you let the icing sit for a few hours, or overnight at best, the color will deepen.
I did an Elmo cake awhile back and just kept on adding the no taste red until I achieved the deep red I was going for.
Hey there! Try adding some burgandy color. It usually works for me. When I worked in a bakery, we used to have a very soft colored choc. icing--light brown and then it would turn into a beautiful red with just red color. It was a whipped icing, so I don't know if it will work with BC. I do the burgandy. Hope that helps......
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