There is a npm package to get system color scheme and detect changes : https://www.npmjs.com/package/@btfcss/system-color-scheme
import systemColorScheme from "@btfcss/system-color-scheme";
// Get system settings
if (systemColorScheme.isDark())
console.log ('System color scheme is dark');
else
console.log ('System color scheme is light');
// Listen for changes
systemColorScheme.addEventListenerOnChange((isDark) => {
if (isDark) console.log("System color scheme changed for dark");
else console.log("System color scheme changed for light");
})