The purpose of your one-sheet is to help the person you leave it with to remember your story so they'll read your screenplay. Whether you give it to them with your script or leave it with them to look at later, your one-sheet plays a very important role in your marketing. Most writers don't even have one-sheets, and if they do, they're boring old black and white type with the wrong graphics. It probably makes people NOT want to read it! Get yours done right!