color.js

var colors = new Array(
  [29,119,239],
  [90,200,251],
  [129,243,253],
  [0,180,160],
  [152,85,212],
  [184,82,158]);


//

var step = 0;
//color table indices for:
// current color left
// next color left
// current color right
// next color right
var colorIndices = [0,1,2,3];

//transition speed
var gradientSpeed = 0.002;

function updateGradient()
{

  if ( $===undefined ) return;

var c0_0 = colors[colorIndices[0]];
var c0_1 = colors[colorIndices[1]];
var c1_0 = colors[colorIndices[2]];
var c1_1 = colors[colorIndices[3]];

var istep = 1 - step;
var r1 = Math.round(istep * c0_0[0] + step * c0_1[0]);
var g1 = Math.round(istep * c0_0[1] + step * c0_1[1]);
var b1 = Math.round(istep * c0_0[2] + step * c0_1[2]);
var color1 = "rgb("+r1+","+g1+","+b1+")";

var r2 = Math.round(istep * c1_0[0] + step * c1_1[0]);
var g2 = Math.round(istep * c1_0[1] + step * c1_1[1]);
var b2 = Math.round(istep * c1_0[2] + step * c1_1[2]);
var color2 = "rgb("+r2+","+g2+","+b2+")";

 $('.gradient').css({
   background: "-webkit-gradient(linear, left top, right top, from("+color1+"), to("+color2+"))"}).css({
    background: "-moz-linear-gradient(left, "+color1+" 0%, "+color2+" 100%)"});

  step += gradientSpeed;
  if ( step >= 1 )
  {
    step %= 1;
    colorIndices[0] = colorIndices[1];
    colorIndices[2] = colorIndices[3];

    //pick two new target color indices
    //do not pick the same as the current one
    colorIndices[1] = ( colorIndices[1] + Math.floor( 1 + Math.random() * (colors.length - 1))) % colors.length;
    colorIndices[3] = ( colorIndices[3] + Math.floor( 1 + Math.random() * (colors.length - 1))) % colors.length;

  }
}

setInterval(updateGradient,20);