Ghosts can be friendly (like Casper) or scary (like every other ghost in history), and with these two manicures you can decide which take you want on your nails. For a friendlier vibe, use a hot pink polish to create smiley mouths on all your ghosts. If you want to go the scary route, stick to the plain black and white — with a twist. Use a glow-in-the-dark nail polish, like Sephora by OPI in Full Moon, $9.50, to paint the ghosts. Now, everyone can see them no matter how dark it gets …