How do I target the css for the fees boxes background color?

Hey koala!

Thank you for using Enfold.

You can use this on Quick CSS or custom.css:

.main_color tr:nth-child(odd), .main_color .pricing-table>li:nth-child(odd), .main_color .pricing-extra, .main_color table caption, .main_color tr:nth-child(even), .main_color .pricing-table>li:nth-child(even) {
background: rgba(0,0,0,.8);
}

.pricing-table .main_color h1, .pricing-table .main_color h2, .pricing-table .main_color h3, .pricing-table .main_color h4, .pricing-table .main_color h5, .pricing-table .main_color h6 {
color: white !important;
}

Cheers!
Ismael