I had a similar problem with unchecked CheckBoxes and RadioButtons.
I found the solution, when I figured out that controls takes their “Off” color from
<item name="android:textColorSecondary">@color/secondary_text</item>
EDIT:
Specifying, if your app’s or activity’s theme inherite one of L’s AppCompat (Dark/Light/Light.DarkActionBar), you can set:
<style name="SampleTheme" parent="Theme.AppCompat">
<item name="colorAccent">@color/green</item>
<item name="android:textColorSecondary">@color/red</item>
</style>
And that’s result:
Notice: When you get different effect you probably use “wrong” theme – make sure you set it correctly.