How to Change Header Background color to white

Hi, i need to change the default header background color to white. It works while scrolling the page to white. But during the initial loading of the page it is transparent. please help

Hi,

Put this CSS code into Customize > additional CSS to add a background color to the menu bar.

.site-header {
    background-color: rgba(255, 255, 255, 0.5) !important;
}

Regards,
Awan