Well that depends on the content of the book i am buying. If the content of the book interests me then i will buy it. It doesn't really matter if the cover of the book is Purple or Pink.
I'm glad you think the way you do, but looks are important too. You don't pick up and read the synopsis of every book you see in a store. You only care about those that look interesting. So what I'm actually wondering is if you would even pick up a book with a "girlish" colour.
I'd use a colour scheme that best represents the key themes.
The novel is about something purple, which is why I'm thinking about making the cover purple too, but, yeah... Is there any good literature on colour psychology that you would recommend? (I've read several guides detailing the dos and don'ts when it comes to designing your own book cover, and most of the don'ts are things that no sane person would ever do anyway, but all they said about colours is that they shouldn't be too aggressive.)