I've never done this before. I tried to apply CMY colorspace theory (cyan-magenta-yellow) to create six colors, but there were two unexpected complications:

1. The cyan spiral arm was almost completely overwhelmed by yellow in some places, forming green with almost no cyan.
2. The magenta spiral arm didn't form properly in some places, forming a "spokes" effect instead.

But I wouldn't necessarily call the result ugly. I've already done two more tie-dyes (including another attempt at this type of pattern) and am letting them set for a good 20 hours before I rinse out the dye and see how they turned out.

I made this using an ordinary 100% cotton T-shirt and Tulip-brand turquoise, fuchsia and yellow dyes, and I soaked the shirt in plain water (with no soda ash) and wrung it out to slightly damp before twisting, tying and dyeing. I'm still a total novice at this, so I don't really know everything I'm doing "wrong" yet.