Update docs

docs/api/system-preferences.md

@@ -7,6 +7,19 @@ const {systemPreferences} = require('electron')
 console.log(systemPreferences.isDarkMode())
 ```
 
+## Events
+
+The `systemPreferences` object emits the following events:
+
+### Event: 'accent-color-changed' _Windows_
+
+Returns:
+
+* `event` Event
+* `newColor` String - The new RGBA color the user assigned to be there system
+accent color.
+
+
 ## Methods
 
 ### `systemPreferences.isDarkMode()` _macOS_
@@ -124,3 +137,16 @@ if (browserOptions.transparent) {
 ```
 
 [dwm-composition]:https://msdn.microsoft.com/en-us/library/windows/desktop/aa969540.aspx
+
+### `SystemPreferences.getAccentColor()` _Windows_
+
+Returns the users current system wide color preference in the form of an RGBA
+hexadecimal string.
+
+```js
+const color = app.getSystemAccentColor() // `"aabbccdd"`
+const red = color.substr(0, 2) // "aa"
+const green = color.substr(2, 2) // "bb"
+const blue = color.substr(4, 2) // "cc"
+const alpha = color.substr(6, 2) // "dd"
+```