I see this thread is a few months old, but I thought I would post the solution in case anyone else comes across this:
This isn’t declared inline exactly. It’s set using jQuery onClick. Since there isn’t a menu provided where colors can be customized, the way to overcome this is to dequeue the js that came with the plugin and enqueue a custom file in your child theme.
If you’re not using a child theme, I would strongly recommend one. It prevents resetting all your changes every time you update.
So, first thing you need to do is go to YOUR-ROOT-DIR/wp-content/plugins/waving-portfolio/assets/js and copy the custom.js file to your child theme. You’ll need to create a folder for it YOUR-ROOT-DIR/wp-content/themes/YOUR-CHILD-THEME/scripts. Now edit your copy of the file and change the color on line 19 to whatever you want.
Once you’ve created a copy of the file in the folder you created, you’ll want to open (or create) your functions.php file in your child theme dir. If you don’t have one yet, create it and make sure there is an open php tag at the top.
Now you want to add this function to dequeue the plugin script and enqueue yours:
/**
* Dequeue Wave Portfolio js to allow for color change
*
* Hooked to the action, with a late priority (100),
* so that it is after the script was enqueued.
*/
add_action('wp_enqueue_scripts', 'wave_portfolio_script_fix', 100);
function wave_portfolio_script_fix()
{
wp_dequeue_script('waving-portfolio-custom-script');
wp_enqueue_script('YOUR-CHILD-THEME-custom-script', get_stylesheet_directory_uri().'/scripts/custom.js', array('jquery'));
}
Make sure to add the name of your child theme on the enqueue line. After that you’re done. Save your function file and refresh your page.