Take a look around line 1757 in your css for this –
.portfolio .more-link {
background: none repeat scroll 0 0 #000;
border-radius: 3px 3px 3px 3px;
color: #fff;
display: block;
font-family: ff-dagny-web-pro;
font-size: 0.875rem;
font-weight: bold;
margin: 20px 0 0;
padding: 5px 10px;
text-align: center;
text-decoration: none;
width: 100px;
}
Looks like everything you’ll need to change is right there. Just let me know if you need help changing any part of the code if you’re not familiar with css.