Responsive sized theme colors

Josh, I tried it in the header css section in general settings>layout>custom css and it works. Will not work in the normal custom css section. Is it ok to place it in the header section along with other css that wont work in the custom box?

<style>.label-success {
background-color: #000!important;
border: 1px solid #ff9e00!important;
color: #fff!important;
}</style>

Cheers, H