Change background color of button in Twitter Bootstrap using CSS

Change background color of button in Twitter Bootstrap using CSS

I am using the following pagination button styles provided by Twitter
Bootstrap:
<ul class="pager">
<li class="previous"><a href="#">&larr; Older</a></li>
<li class="next"><a href="#">Newer &rarr;</a></li>
</ul>
This is how they currently look like:

How do I need to change my CSS style to change the background color of
these buttons from green to some other color?
I tried this CSS code, but it did not change the button styles:
.next {
background-color: #ecf0f1;
color: #2d525d;
}
Thank you!