<?php
/*
WARNING :
  https://github.com/Automattic/amp-wp
    needed
*/

add_action( 'amp_post_template_css', 'xyz_amp_my_additional_css_styles' );

function xyz_amp_my_additional_css_styles( $amp_template ) {
    // only CSS here please...
    ?>
    .amp-wp-byline amp-img {
        border-radius: 0; /* we don't want round avatars! */
    }
    .amp-wp-header {
      <!-- background-color: #FBBA00; -->
    }
    a, a:visited, .amp-wp-comments-link a {
      <!-- color: #FBBA00; -->
    }
    <?php
}
