The latest Chrome Beta release, version 76, supports a CSS option called "prefers-color-scheme." When this option is enabled, websites that usually show a white background and black text may switch to a black background and white text (and vice versa). As it's linked to your Chrome (or even your OS) dark mode preference, you don't need to toggle anything as the website will handle everything for you.
Google has been slower than other companies to embrace dark mode, though it did add the feature to Chrome 73 beta for Android in February and Chrome 74 beta for Windows in March. It's available to Chrome users on all the major platforms: Android, Chrome OS, Linux, macOS and Windows.
In addition, Chrome 76 beta also includes number of important updates. In a move everyone saw coming, Flash is now blocked by default and websites will no longer be able to detect users browsing in Incognito mode.