Hi Fran,
Sorry to getting you back late.
That is how it is coded inside the plugin, can you try something like this in your functions.php last line before ?>
add_action('woocommerce_email_header', 'add_css_to_email');
function add_css_to_email() {
echo '
<style type="text/css">
#template_header h1 { color: blue; }
</style>
';
}
If that didn’t work, try to put !important, if that also didn’t work you need to do something like this that stated in that area “For more advanced control copy woocommerce/templates/emails/ to yourtheme/woocommerce/emails/.”
Let me know, what you got.
Thanks,
laranz.