E-books don’t need color screens. They just don’t. The novel, as it exists on paper does not use color. When you read a book on a Nook or a Kindle, you definitely don’t need color to enjoy the story. However, the novels of the future will use color and more importantly, they will use the web. They will use color, because they will have hyper links and pictures and maybe, videos.
The novels of the future will not be linear as they are now. They will be living documents. They will have fans and the fans will have their own endings and maybe even their own characters. It may be that all the author does is create a universe and populate it with some key characters. It will be the readers who decide how the story goes. Much like modern video games.
Even if the linear story survives, it will be enhanced with layers and layers of information about the story, the reader and even where the reader lives. The book may even become a destination instead of a story. My kids read age appropriate versions of classic novels. As they grow into them, they might in the future turn into the actual novel that the author wrote, to reflect the new age of the reader.
All aspects of a story could drastically change the form of the novel as we know it now. But an e-book with a color screen will change nothing. Nothing.