add_action( amp_post_template_css,xyz_amp_additional_css_styles );
function xyz_amp_additional_css_styles( $amp_template ){background:#000}nav.amp-wp-title-bar a{background-image:url('https://adviceboxcom.files.wordpress.com/2016/07/advicebox_logo_home.png');background-repeat:no-repeat;background-size:contain;display:block;height:28px;width:94px;margin:0 auto;text-indent:-9999px}