You would have to put a class or an id on the element that contains your phrase, then put all your styling in the EXTRA.css template.
Example.....
in footer template....
<span class="my_footer_phrase">{xen:phrase footer_text}</span>
then in EXTRA.css...
.my_footer_phrase
{
font-size: 1em;
font-weight: 600;
color: #808080;
}