Unless you want to look like you woke up on the wrong side of the '90s, never do this! Obvious lip boundaries marked with bold colors is so out of style and borderline vulgar. Don't be mistaken, you can use a lip contour pencil, but you must also use an identically colored lipstick to fill in the rest of your mouth. The point is to try and make your lips look fuller naturally, not draw attention to the fact that you're trying. Avoid creamy lipstick or gloss, which tends to come off easier than long-wearing lipstick and will likely leave the stamp of your lip contour behind.