If you want to to customize Add to Cart Button Color in WooCommerce, just follow these steps

1. Add to Cart Button Color on Product Page

Just insert this code (Lines 02 – 16) into Appearance > Customize > Additional CSS (or Custom CSS)

2. Add to Cart Button on Product Category

Just insert this code (Lines 18 – 30) into Appearance > Customize > Additional CSS (or Custom CSS)

Done!