I mix my own red for painting my models with, especially my Eldar. It's a mix of Reaper Mini blood red (not the GW variety), Red Gore, Brown Ink and Red Ink. I can't really explain how much of each, as I tend to just mix it by sight, but if you are going to try it yourself I suggest you go heavy on the inks - especially the brown - and keep it nice and watery because you want it to sink into the cracks.
The reason I'm mentioning this is because I just love how it's turning out. This isn't a pat on the back for me, mind you; paint does as it will and I was just lucky to get the right combination. What I will say, however, is taht it's the most beautiful red I've ever put on a model. You'll notice from the picture below that the brown automatically and naturally shades the lines while the lush, bloody red stays on the surface and gives very, very soft and natural highlights. I just love staring, because the model it's applied to is also gorgeous and the two make a really nice picture.
Problem is that now I don't want to paint anything else on it to ruin the effect of the red. Sigh.