<!-- for a singular color regardless of theme -->
<meta name="theme-color" content="#ffffff">
<!--Different ones for light and dark theme if your website supports them: -->
<meta name="theme-color" content="#ffffff" media="(prefers-color-scheme: light)">
<meta name="theme-color" content="#000000" media="(prefers-color-scheme: dark)">
<!--source: https://developer.apple.com/forums/thread/683403 --><meta name="theme-color" content="#ffffff"><!-- Theme-color is use to set the background to your favorite/Branding color
Add two attribute in meta tag first 'name="theme-color"' and second 'content="Your Hexadecimal Code"'
Add Below Meta property to your HTML code in HEAD Section -->
Example:
<head>
...
<meta name="theme-color" content="#444444">
...
</head>