Refer to first occurrency of element with classname “foobar”?

[pstein]

Assume the following code:

<div class="foobar" ....>   // target
   <div class="foobar" ...>....</div>
</div>
<div class="foobar" .... >....</div>

Now I want to assign a new CSS rule to only the first element which has the class “foobar”. In the sample above the

with “target” as comment.
How can I address this?

[foobar]:first { color: red }

or

.foobar:first { color: red }

do not work