My favorite's always been Yellow. Though that's just the basic seven colors. My favorite metallic colors are Silver and Gold.
Speaking of which, you may have noticed how I just treated the color variations as separate. Well you see, it annoys me when someone is asked what their favorite color is and they respond with a different shade of a basic color that Crayola gave a stupid name to, such as Robin's Egg Blue, or Tickle Me Pink, some such crap.