Why is Alice Walker's novel entitled The Color Purple, and what does it have to do with beauty?
In addition to all of those connotations, purple also calls to mind bruises, and the protagonist of this novel suffers many, both literally and figuratively. It is the relationship between the bruise and the hope, the suffering and the rich nature of her life, that comprise the meanings of the title.
Purple stands for hope, and one of the great miracles of this book is that anyone who lived through it (like Celie) could find any hope at all.
It is the beauty of the rare, the miraculous, the unlooked for. (Traditionally, purple was also associated with royalty and riches.)