Create a xml named colors.xml in res/values folder:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="red">#ff0000</color>
<color name="green">#00ff00</color>
</resources>
In drawable folder, create a xml file my_btn_toggle.xml:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="false" android:drawable="@color/red" />
<item android:state_checked="true" android:drawable="@color/green" />
</selector>
and in xml section define your toggle button:
<ToggleButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New ToggleButton"
android:id="@+id/toggleButton"
android:background="@drawable/my_btn_toggle"/>