Generate Random Hex Color Example: http://codepen.io/garystorey/pen/ugtza

randomcolor.js

var randomColors = {

	init : function () {
		this.elems = document.querySelectorAll("div");
		this.update();
    document.querySelector('#updateColors').addEventListener('click', function() {
      randomColors.update();
    });
	},
  
	update : function () {
		var b, c, i = 0, el;
		for (; el = this.elems[i]; i++) {
			b = this.randomColor();
			c = this.useBlackOrWhite( b );
			el.style.color = '#' + c;
 			el.style.backgroundColor = '#' + b;
 			el.style.borderColor = '#' + c;
 			document.getElementById( 'bg' + i ).value = '#' + b;
		}
	},
	randomColor :  function () {
	  var vals = ['0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'],
    	  len = vals.length, r = 0, color = new Array(5);
  
    for (; r < 6; r++) { color[r] = vals[ this.randomNumber( len ) ]; }
    return color.join('');
  },
	randomNumber : function ( len ) { return Math.floor(Math.random()*len);	},
	useBlackOrWhite : function ( hexcolor) {  /* from 24 Ways */
		var r = parseInt( hexcolor.substr(0,2), 16 ),
		    g = parseInt( hexcolor.substr(2,2), 16),
		    b = parseInt( hexcolor.substr(4,2), 16),
	    	yiq = (( r*299 )+( g*587 )+( b*114 )) / 1000;
		return (yiq >= 128) ? '111' : 'eee';
	}

};
randomColors.init();