Procure por:
]]></b:skin>
e acima dele cole o seguinte código:
.blog-pager {
background: #000;
padding: 8px 3px 8px 3px;
}
.blog-pager a{
color: #000;
}
.blog-pager-older-link, .home-link,
.blog-pager-newer-link {
-webkit-border-radius: 2px;
-moz-border-radius: 2px;
border-radius: 2px;
background: -webkit-gradient( linear, left top, left bottom, color-stop(.2, white), color-stop(1, #E5E5E5) );
background: -moz-linear-gradient( center top, white 20%, #E5E5E5 100% );
font: 11px/18px sans-serif;
padding:6px 8px; margin:10px 3px 10px 3px;
}
Caso queira trocar a cor edite as partes destacadas em vermelho.
