Array intersection: an array of values which occur in each of the passed arrays. Does the right thing with empty arrays.

gistfile1.txt

var palette1 = ("white,green,brown,blue,orange").split(','),
  palette2 = ("cyan,orange,black,white").split(','),
	palette3 = ("black,white,grey").split(',');

// given one or more arrays of values,
// return an array with only those values present in each
function intersection() {
  var lists = Array.prototype.slice.call(arguments);
  return lists.reduce(function(aCommon, aValues){
    var overlap = aValues.filter(function(val){
      return aCommon.indexOf(val) > -1;
    });
    return overlap;
  }, lists.shift());
}

console.log('result: ', intersection(palette3, palette2, palette1));