Change "on" color of a Switch

As of now it is better to use SwitchCompat from the AppCompat.v7 library. You can then use simple styling to change the color of your components.

values/themes.xml:

<style name="Theme.MyTheme" parent="Theme.AppCompat.Light">
    <!-- colorPrimary is used for the default action bar background -->
    <item name="colorPrimary">@color/my_awesome_color</item>

    <!-- colorPrimaryDark is used for the status bar -->
    <item name="colorPrimaryDark">@color/my_awesome_darker_color</item>

    <!-- colorAccent is used as the default value for colorControlActivated,
         which is used to tint widgets -->
    <item name="colorAccent">@color/accent</item>

    <!-- You can also set colorControlNormal, colorControlActivated
         colorControlHighlight, and colorSwitchThumbNormal. -->

</style>

ref: Android Developers Blog

EDIT:

The way in which it should be correctly applied is through android:theme="@style/Theme.MyTheme" and also this can be applied to parent styles such as EditTexts, RadioButtons, Switches, CheckBoxes and ProgressBars:

<style name="My.Widget.ProgressBar" parent="Widget.AppCompat.ProgressBar">

<style name="My.Widget.Checkbox" parent="Widget.AppCompat.CompoundButton.CheckBox">

Late to party but this is how I did

Style

 <style name="SCBSwitch" parent="Theme.AppCompat.Light">
        <!-- active thumb & track color (30% transparency) -->
        <item name="colorControlActivated">#46bdbf</item>

        <!-- inactive thumb color -->
        <item name="colorSwitchThumbNormal">#f1f1f1
        </item>

        <!-- inactive track color (30% transparency) -->
        <item name="android:colorForeground">#42221f1f
        </item>
    </style>

Colors

Layout

<android.support.v7.widget.SwitchCompat
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:checked="false"
    android:theme="@style/SCBSwitch" />

Result

See change of colors for enables and disabled switch