Kool aid dying works beautifully for wool yarn but unfortunatly you have to you acid dyes for silk. It is beautiful when finished but a little more involved. As for the color changes you can “paint” your yarn by dipping it or pouring the dye on the yarn http://www.yarndreams.com/dye.html Good link for Kool-aid dyeing
I’ve actually had success using Wilton dyes on silk – you do have to soak it in vinegar water first, and for a long time – silk takes a long time to get thoroughly wet, and if it’s not completely wet it won’t take the dye evenly. The colors are so beautiful and vibrant!