Higgins Fadeproof Ink is available at art and craft type stores. I used it on my Baby Magician to very good effect! I diluted it with wood alcohol and stained the wood first then put some in the dope. Very even and deep color resulted.
However, I have discovered that there are powdered analine dyes available at the "pro" woodworking stores. These dissolve well in wood alcohol, and then can be used as part of the thinner in dope! As Andy B found out, filter the dyed alcohol before using! The color is really intense, and pretty good fade resistance.
I intend to dye silk or silkspan with the straight alcohol/dye mix, then add the remainder to the dope next time I do that kind of finish.