In case you are working in the latest toolbar in android studio then here is the smallest solution To change the toolbar options menu color, add this to your toolbar element
app:popupTheme="@style/MyDarkToolbarStyle"
Then in your styles.xml define the popup menu style
<style name="MyDarkToolbarStyle" parent="ThemeOverlay.AppCompat.Light">
<item name="android:colorBackground">@color/mtrl_white_100</item>
<item name="android:textColor">@color/mtrl_light_blue_900</item>
</style>
Note that you need to use colorBackground not background. The latter would be applied to everything (the menu itself and each menu item), the former applies only to the popup menu.