Are you going for the dark blood red? Also, will you be using it for transparent soap or solid?
Natures Garden has a red oxide that is pretty dark, but I think it would be even darker if you mixed a little brown oxide with it.
But if you're just mixing it in white mp, it will not turn the dark red you're looking for. Mix it with clear mp to a little darker than what you're looking for, then add just enough white mp to make it nontransparent.
I use this http://www.goplanetearth.com/colors_other.html (the tomato red)
it produces a true bright red in clear m&p that doesn't bleed.
If I wanted it blood red, I'd add a little red oxide or burgundy mica to it.