function makearray(n) {

  this.length = n;

  for(var i = 1; i <= n; i++)

    this[i] = 0;

  return this;

}



hexa = new makearray(16);var ptstep=0;

for(var i = 0; i < 10; i++)

  hexa[i] = i;

  hexa[10]="a"; hexa[11]="b"; hexa[12]="c";

  hexa[13]="d"; hexa[14]="e"; hexa[15]="f";

  function hex(i) {

  if (i < 0)

    return "00";

  else if (i > 255)

    return "ff";

  else

    return "" + hexa[Math.floor(i/16)] + hexa[i%16];

}



function setbgColor(r, g, b) {

  var hr = hex(r); var hg = hex(g); var hb = hex(b);

  document.bgColor = "#"+hr+hg+hb;

}



function cycle(sr, sg, sb, er, eg, eb, step) {

  setbgColor(

   Math.floor(sr * ((step-ptstep)/step) + er * (ptstep/step)),

   Math.floor(sg * ((step-ptstep)/step) + eg * (ptstep/step)),

   Math.floor(sb * ((step-ptstep)/step) + eb * (ptstep/step)));

  ptstep+=1;

  if (ptstep<=step) {

   var chaine="cycle("+sr+","+sg+","+sb+","+er+","+eg+","+eb+","+step+");"

   setTimeout(chaine,50);

  }

}