I still question the validity of this symbol meaning "purple."
In high school, we had twin exchange students FROM China. Both told me that it wasn't a Chinese character at all, and that it was just a symbol that resembled Chinese writing. "It doesn't mean 'purple'?" I asked. One of them then took out a notebook and drew the character for 'purple' - which did not even slightly resemble the doo-dad on the front of STP's Purple.
Having not been satisfied with this answer, I later asked this same question to a Japanese student in college. He said it absolutely was not Japanese. He didn't know what it was, but he knew it wasn't Japanese.
This question comes up every few years, usually because someone wants a tattoo.
Art School Boy - don't put a Chinese/Japanese symbol on yourself, even if it IS STP. It's so fucking trendy. All these douchebags are walking around with Chinese writing that stands for "power," and "truth," and "strength" -- when in reality they probably aren't Chinese characters at all, or they mean something entirely different. I say unless you speak the language and KNOW FOR A FACT what it means, you shouldn't ink it to yourself. It COULD say "smelly monkey balls." And you'd never know.
Personally, I don't believe that the symbol on the front of the album is anything more than just a design.