MetaExtension theme-color
Is used to brand the address bar of a website (only on mobile devices) in a selected Hex-color.
Read more about theme-color on Googles Developer Portal (opens in a new tab) or in the HTML Specification (opens in a new tab).
Usage
<meta name="theme-color" content="#317EFB">content can be any valid Hex-color or CSS color-value.
There can also be a media-attribute added to define in which system-color-scheme which color should be used for the address bar:
<meta name="theme-color" content="#317EFB" media="(prefers-color-scheme: dark)">theme-color is defined in the HTML Specification (opens in a new tab) and is therefore a HTML Standard.