CSS an element that has Multiple Classes

Best to show with an example:

<p class="classone">some text</p>
<p class="classtwo">some text</p>
<p class="classone classtwo">some text</p>

<style type="text/css">
.classone{
  color:#FF0000;
} 
.classtwo{
  color:#00FF00;
} 
.classone.classtwo{ 
  color:#0000FF;
} 
</style> 

Preview:

some text

some text

some text