Unable to change switch color

Probably, you can try using android.support.v7.widget.SwitchCompat instead of Switch and android:theme=@style/SwitchStyle instead of style="@style/SwitchStyle"

You're mixing styles and themes together.

These attributes are theme attributes so define them together in a theme overlay:

res/values/styles.xml (not values-v21)

<style name="ThemeOverlay.MySwitch" parent="">
    <item name="android:colorControlActivated">@color/switch_color</item>
    <item name="android:colorSwitchThumbNormal">#f1f1f1</item>
    <item name="android:colorForeground">#42221f1f</item>
</style>

<style name="ThemeOverlay.MySwitchCompat" parent="">
    <item name="colorControlActivated">@color/switch_color</item>
    <item name="colorSwitchThumbNormal">#f1f1f1</item>
    <item name="android:colorForeground">#42221f1f</item>
</style>

And then apply this theme overlay on the switch:

res/layout/layout.xml

<Switch
    android:theme="@style/ThemeOverlay.MySwitch"/>

<androidx.appcompat.widget.SwitchCompat
    android:theme="@style/ThemeOverlay.MySwitchCompat"/>

Pick one of the two variants:

• Switch available since API 21, all theme attributes are prefixed with android:
• SwitchCompat available in AndroidX AppCompat library, some theme attributes are not prefixed (make sure you know which).