There are a lot of publications, that the bark of Jatropha Curcas contains 37% tannin and yields a dark blue dye, which is used for colouring cloths, fishing nets and lines( under 7.5http://www.tifac.org.in/news/Bioenergy_1.htm ).But the only site describing the preparation is this one:http://www.wigsat.org/gasat/papers1/19.txt, where you find under "procedure for making gara" and "preparation of the dye bath" a mixture of several plants incl. Jatropha.Could be the method works without the other ingredients too.