code: function nextColor(pos, start, finish) {
      var r = [], i, e, from, to
      for (i = 0; i < 6; i++) {
        from = Math.min(15, parseInt(start.charAt(i),  16))
        to   = Math.min(15, parseInt(finish.charAt(i), 16))
        e = Math.floor((to - from) * pos + from)
        e = e > 15 ? 15 : e < 0 ? 0 : e
        r[i] = e.toString(16)
      }
      return '#' + r.join('')
    }
docs: this gets you the next hex in line according to a 'position'