Where to change the background color of this SPAN.label.es-stream-type ?

I want to change the color of this label and the others on the stream feed, but i can't find any occurence in the css files.
It's seems to be somewhere in the html rendered by PHP:

 <span class="label es-stream-type" style="background: none repeat scroll 0% 0% rgb(22, 22, 211);">



    Article



</span>