To add volume to the lips without having to go under the knife, try some strategically placed lip gloss. You don’t have to apply gloss all over the lips, which is especially great for those of us that aren’t lip gloss kind of girls. Just concentrate a bit of gloss on the middle of the bottom lip and blot. Apply a couple more layers if desired. The gloss will reflect light (rather than absorb light as a matte colour does) and help to create the illusion of fuller lips.
To play down the lip volume, opt for a flattering colour at least 2 shades darker than your own lips. Darker colours will make lips appear smaller by doing the opposite of gloss and not reflecting light. Avoid the use of gloss to minimize the appearance of lip size.