Dune is a classic sci-fi novel from the 60's. There are many underlying religious tones in the book. That's where the red hand comes from. It is also the color of the "spice," which is a key factor in survival for the people of the planet this book takes place on. In the book, their religious text comes from the fictional Orange Catholic Bible. The hand comes from the Red Hand of Ulster flag from Ireland, and the Irish being mostly Catholic, the red hand fits in the book. There is also a part in the book where the main character, Muad'dib smears the spice over the soldiers, and displays his right hand to his army.