#filters li a{

    font-family: Roboto;
    line-height: 25px;
    font-weight: 300;
    font-style: normal;
    font-size: 15px;
}

change attributes you want and add the code to customize css

in portfolio-page.php change line 72 from

<li><a href="#" data-filter=".<?php echo sanitize_title( $portfolio_cat->slug ); ?>"><?php echo sanitize_title( $portfolio_cat->name ); ?></a></li>

to

<li><a href="#" data-filter=".<?php echo sanitize_title( $portfolio_cat->slug ); ?>"><?php echo wp_kses_post( $portfolio_cat->name ); ?></a></li>