My workplace is corporate and very conservative. (You don't see men wearing crazy ties much less women in sassy earrings.)
Yet, every once in a while, I will get an email with a "fun" signature. I have to admit: I usually pause and pass judgment on the person.
I wonder if I am the only stick in the mud who thinks this sort of "flourish" is risky when it comes to keeping up a professional persona, i.e., your own "brand" at work? To me, it's the email equivalent of wearing dangly, light-up earrings on a day when you have a client meeting. In sum, it's not a good idea if you want to be taken seriously.
Deborah Tannen talks about how women can't simply dress for work, but instead, women always convey a certain "look," e.g., sophisticated, conservative, sexy, etc. In getting dressed, women have many choices to make, from shoes to accessories to hair style. There are several variables at play here, and each conveys a ton of meaning. She calls this "marked."
(For more on the notion of "marked"/"unmarked," read this article: The New York Times Magazine, June 20, 1993. "Wears Jump Suit. Sensible Shoes. Uses Husband's Last Name." Originally titled "Marked Women, Unmarked Men" by Deborah Tannen)
Back to the email signature. A purple signature is "marked" in much the same way. The default ("unmarked") is to keep your signature in black/white and an "unmarked" font, e.g., Arial, or whatever the body of the email is in. At best, it's a "fun" flourish, at worst, it could take away from your image as a professional.
(As an aside, I am learning about the field of information visualization. It encompasses graphic design, brain science, and communication. I wonder if there's some research in this field that could explain my prejudice against the purple, scripty signature?)