Hi there!

Thanks for reaching out to us.

Here is the sample custom CSS for you:

.sp-megamenu-parent .sp-dropdown li.sp-menu-item>a {
    color: red !important;
}

You can use any colors of your choic in the above code.

Here is all about custom code placement in Helix Ultimate: https://www.joomshaper.com/documentation/helix-framework/custom-code-css-js-meta

Best Regards

Thanks!