When it comes to dyeing, there is one thing you must know about your fabric: fiber content. The chemical makeup of the fiber determines which types of dyes can be used successfully. Protein, or animal-based, fibers such as wool and silk dye best with acid-based dyes.
The easiest acid dyes to use on silk for tie-dyeing are those that do not require steaming to set the colors. These dyes are formulated as an “instant set” dye, or they use a chemical additive to set the color. Colorhue by Ginny Eckley silk dyes (available at MakeScreens.com and other sites), are premixed, instant-set dyes that only need to be diluted with water to the desired intensity. Jacquard Silk Colors or Jacquard Green Label, and Tinfix Design, by Sennelier (all available at DharmaTrading.com), can be mixed with a chemical dyeset fixative that eliminates the need for steaming to set the colors.
You can try using a dye not intended specifically for silk, but the result is usually a non-colorfast stain rather than a true dye. Dyes intended to work on multiple fiber types yield unpredictable results and usually do not have the intensity, washfastness, or lightfastness that specialty dyes produce.