Do you think blue eyeshadow automatically means permed hair, mullets and matching frosted pink lips? Stop. Blue liner (or subtle shadow!) actually brings out the whiteness of eyes, making you look more awake and really flattering brown and green eyes in particular.
You can draw it on the upper lashline, or be a bit more daring and draw it along the inner rim of the lower lashline. If you keep the rest of your makeup au naturale, it will be your feature look!