Hi there!

Thanks for contacting us! Sorry to say that our site is our own customization, and customization support is prohibited here. However I'm not sure which effect you are talking about!

Would you please look into our templates from here if any of them suits you: https://www.joomshaper.com/joomla-templates

And here is the process how to create custom header: https://www.youtube.com/watch?v=bYPgWAWzXpM

Best Regards

Hi, It's based on CSS only. Example code:

#sp-header.header-sticky {
    background: rgba(255, 255, 255, 0.9);
}

Extra tips: https://www.joomshaper.com/documentation/helix-framework/helixultimate/faq-how-to-do