Paul

You may choose a colourful style for the custom coupon message, or wrap the message in your own CSS class container.
It’s also possible to hide the default message from Woocommerce so that only your custom coupon message is displayed. 
(the plugin uses inline CSS to hide the default Woocommerce message).
Take a look at the screenshots for the coupon edit screen with the plugin enabled and some examples.
The meta box was implemented using the technique described on this blog post: 
http://wp.smashingmagazine.com/2011/10/04/create-custom-post-meta-boxes-wordpress/
The message styles were generated using this tool: 
http://www.bestcssbuttongenerator.com/

Woocommerce Custom Coupon Message

This plugin adds a meta box to the coupon edit screen where you can make your own customized coupon message.

Soft79

“Extended Coupon Features for WooCommerce” adds functionality to the WooCommerce coupons and allows for automatic discount rules. 
Very easy to use, the functionality is conveniently integrated to the WooCommerce Edit Coupon panel.
Requires: 
* WordPress 5.0 or newer (6.8+ recommended) 
* WooCommerce 5.0 or newer (9.0+ recommended) 
* PHP 7.0 or newer (8.2+ recommended)
Full documentation is available at <a href="http://www.soft79.nl/documentation/wjecf" rel="nofollow ugc">www.soft79.nl</a>.
<ul>
<li>Auto coupons: Allow coupons to be automatically added to the users cart if its restrictions are met,</li>
<li>Apply coupon via an url,</li>
<li>Restrict coupon by shipping method,</li>
<li>Restrict coupon by payment method,</li>
<li>Restrict coupon by a combination of products</li>
<li>Restrict coupon to certain customer roles</li>
<li>(PRO) Add free products to the customer’s cart based on coupon rules</li>
<li>(PRO) Allow a cart discount to be applied based on quantity / subtotal of matching products</li>
<li>(PRO) Set Auto Coupon priorities (Useful for ‘Individual Use Only’-coupons)</li>
<li>(PRO) Restrict coupon by shipping zone</li>
<li>(PRO) Allow coupon for first purchase only</li>
<li>(PRO) API to allow developers to use functions of this plugin</li>
</ul>
For more information or the PRO version please visit <a href="http://www.soft79.nl" rel="nofollow ugc">www.soft79.nl</a>
<h4>Example: Auto coupon</h4>
Let the customer have a discount of $ 5.00 when the cart reaches $ 50.00.
<ol>
<li>Create a coupon, let’s name it auto_50bucks and enter a short description e.g. $ 50.00 order discount</li>
<li>On the General tab: Select discount type Cart discount, and set the coupon amount to $ 5.00</li>
<li>On the Usage restrictions tab: Set minimum spend to $ 50.00 and check the Auto coupon-box</li>
</ol>
Voila! The discount will be applied when the customer reaches $ 50.00 and a descriptive message will be shown.
If the restrictions are no longer met, it will silently be removed from the cart.
<h4>Example: Apply coupon via an URL</h4>
Apply coupon through an url like this:
<ol>
<li>Use the url www.example.com/url-to-shop?apply_coupon=my_coupon&fill_cart=123</li>
</ol>
Voila! Any coupon can be applied this way. Please note that an empty cart can not contain any coupons. Download the free <a href="https://www.soft79.nl/product/cart-links-for-woocommerce/" rel="nofollow ugc">Cart Links for WooCommerce-plugin</a> to handle the ‘fill_cart’-part of the url.
This plugin has been tested in combination with <a href="https://wordpress.org/plugins/wp-multilang/" rel="ugc">WP-Multilang</a>.

Extended Coupon Features for WooCommerce FREE

Excellent Plugin!

Additional functionality for WooCommerce Coupons: Allow discounts to be automatically applied, applying coupons via url, etc...

Woocommerce Custom Coupon Message vs Extended Coupon Features for WooCommerce FREE