MAC's rule is party on the lid (brights and bolds), but business (neutrals) in the crease. MAC calls it the prime look. Pick a color for the crease that matches your skin tone, and blend your lid color up into it and brow highlight down into it. The prime color is also referred to as the "best friend" color. I am NW15. I use Wedge, Malt, Era, Haux, Cork, and Saddle in my crease as prime colors. I apply with the 217 in little circles, then blend in a windshield wiper motion, for a wash of color. The 222 and 224 can be used, too. I use Vanilla or Orb as my brow highlight.