CSS cancel property by overriding class

CSS cancel property by overriding class

I have following html:
<div class="red placeholder"></div>
<div class="blue placeholder"></div>
<div class="green placeholder"></div>
and CSS:
.placeholder {
width: 100px;
height: 100px;
margin: 10px;
border: 1px solid black;
}
.placeholder:hover {
background-color: gray;
}
.red { background-color: red; }
.blue { background-color: blue;}
.green { background-color: green;}
I should not change initial placeholder declaration(s) and I don't want
DIVs to change colour on hover. Is there any way I can override
placeholder class to "cancel" or turn off that hover property?
jsFiddle: http://jsfiddle.net/8QJEq/4/