How to customize template style? – Woo Invoice

    To change the styles (color, size, etc) of the Woo Invoice templates, you have to use the action hook woo_invoice_custom_style. See the example below about how to change the background color of the invoice: 

    add_action('woo_invoice_custom_style', 'woo_invoice_custom_background');
    function woo_invoice_custom_order_number_style() {
        ?>
    
        body{
           background-color: #c2c7ce;
        }
    
        <?php
    }

    To make the order number bold, see the example below:

    add_action('woo_invoice_custom_style', 'woo_invoice_custom_order_number_style');
    function woo_invoice_custom_order_number_style() {
        ?>
    	
        .order-data-table tbody tr:nth-child(2) td{
            font-weight: bold;
        }
    
        <?php
    }