–Save This Script as "stay open applet" to try.

on run
　　current application’s NSDistributedNotificationCenter’s defaultCenter()’s addObserver:me selector:"darkModeChanged:" |name|:"AppleInterfaceThemeChangedNotification" object:(missing value)
end run

on quit
　　current application’s NSDistributedNotificationCenter’s defaultCenter()’s removeObserver:me |name|:"AppleInterfaceThemeChangedNotification" object:(missing value)
　　continue quit –超重要
end quit

on darkModeChanged:(aNotification)
　　set curMode to (my currentDarkMode:"test") as string
　　display notification curMode
end darkModeChanged:

on currentDarkMode:(aNotification)
　　tell application "System Events"
　　　　tell appearance preferences
　　　　　　set curMode to (dark mode)
　　　　end tell
　　　　
　　　　if (curMode as boolean) = true then
　　　　　　return "Dark"
　　　　else
　　　　　　return "Light"
　　　　end if
　　end tell
end currentDarkMode: