Chances are, when you apply eyeliner, you use it to create definition along your upper lash line. You may add a bit to your inner rims, but otherwise you don't touch your lower lash line.
However, if you want to spice things up a bit, you may want to try a bold, colorful line along your lower lashes. It's an easy, sexy way to try something a bit different. Allure magazine suggests starting out by using a purple shade of eyeliner, like Colorescience – Genie Matte Colore in Violets are Blue. The shade is flattering on every eye shade and complexion, so it's pretty foolproof.
Use a black eyeliner pencil to line the rims of your eyes first, then create a thick line of it along your upper lash line. A hint of shimmery shadow, like you'd find with Too Faced – Eye Shadow Duo, should go all over your lids.
Apply the purple liner along your bottom lids, then use a cotton swab to clean up any excess. A touch of mascara is all you need, then you're done!