yige.org 试一个

<!DOCTYPE html>
<html>
<head>
<style> 
div
{
width:100px;
height:100px;
background:red;
animation:myfirst 5s;
-moz-animation:myfirst 5s; /* Firefox */
-webkit-animation:myfirst 5s; /* Safari and Chrome */
-o-animation:myfirst 5s; /* Opera */
}

@keyframes myfirst
{
0%   {background:red;}
25%  {background:yellow;}
50%  {background:blue;}
100% {background:green;}
}

@-moz-keyframes myfirst /* Firefox */
{
0%   {background:red;}
25%  {background:yellow;}
50%  {background:blue;}
100% {background:green;}
}

@-webkit-keyframes myfirst /* Safari and Chrome */
{
0%   {background:red;}
25%  {background:yellow;}
50%  {background:blue;}
100% {background:green;}
}

@-o-keyframes myfirst /* Opera */
{
0%   {background:red;}
25%  {background:yellow;}
50%  {background:blue;}
100% {background:green;}
}
</style>
</head>
<body>

<div></div>

<p><b>注释：</b>当动画完成时，会变回初始的样式。</p>

</body>
</html>
结果:
编辑上面的代码，点击查看结果。
yige.org - 试一个