I've never had fondant that didn't turn teeth red lol but when I make fondant, I start with a pink base, it is easier to get to red from pink. If you start with white, and add red, you're only going to get various shades of pink, and even after it sits, it won't be red.
As ypierce82 said start with a different color base. Depending on what shade red you want that base could be pink, yellow, orange or even lavendar. That cuts down on the amount of red needed therefore will cut the staining and off-taste some. This is true for most any strong/primary color.
Quote by @%username% on %date%
%body%