I have to tint my buttercream icing a blood red color and I am worried about getting an aftertaste to it. Is there a trick to adding something other than the gel colors that will help?

Just use the no-taste red from Wilton. You can also add a tiny bit of black to make it darker.

I always use pink to get a good color in and then either use Wilton No Taste Red or Americolor's Red. Works great and leav it set for about 1/2 hour and you will see that it has darkened up. If not the shade you need just add some more red and a teeny bit of black to darken.