CSS

-webkit-background:linear-gradient(left,red,blue);
-moz-background:linear-gradient(left,red,blue);
-ms-background:linear-gradient(left,red,blue);
-o-background:linear-gradient(left,red,blue);
background:linear-gradient(left,red,blue);

JS

style.webkitTransitionDuration =
style.MozTransitionDuration =
style.msTransitionDuration =
style.OTransitionDuration =
style.transitionDuration = speed + 'ms';