Salivador,
There are several dark mode settings. And do you want to set them or read them?
Most devices now have light/dark mode. Chrome and other browsers have a light and dark mode settings, and, now with AppStudio 8.4 (I believe), the new BootStrap 4 controls have their own dark mode setting.
Setting the device dark mode would be a plugin. Setting Chrome setting is an extension. BootStrap dark mode is soo new I haven’t had time to look at it, so my app is “darkless” for the time being.
This post Detecting Device Dark Mode setting may have some helpful information. Search this board for dark mode for some other posts that may be helpful.