The WooCommerce Button styling in Divi is not the best. You can end up with simple issues of contrasting colour when you style your button.
For some reason, the elegant themes team have decide to not provide any styling specific items for the WooCommerce Buttons or Form Buttons so we are left to do custom CSS.
Because we do have a place to put that css it is relatively easy to deal with pasting in the code to fix the styling issue.
Watch over the screencast to understand how it all works.
The code is found in GIST as usual to fix this WooCommerce Button issue but you can also grab it below.
Remember to look over the CSS and make any adjustments you need for your particular website.
Check out the video on Youtube or follow our blog to get more tweaks of the week, where we help users of Divi and WordPress to make simple fixes for your website.