Check WordPress user and add Admin Styles

functions.php

<?php

global $current_user;
get_currentuserinfo();

function inject_admin_styles() {
     echo '<style type="text/css">#menu-posts {display:none;} </style>';
}

if ($current_user->user_login !== 'admin') { //replace this with your admin user
   add_action('admin_print_styles', 'inject_admin_styles', 11 );
}