Here is the code being used currently:
#previous, #previous a, #previous a:visited, #next-post, #next-post a, #next-post a:visited {
color: #929292;
font: 12px tahoma;
text-decoration: none;
}
You can modify the color and font, and reinsert the code into your child theme style.css file, or into the custom css box via the admin graphene options page.