#How to change background of Material Button
Android Design Patterns, Medium, Medium
The first one works. The other two don't but stiff leave there for reference purposes.
Create this theme in res/values/styles.xml
<style name="RewardRedeemButtonTheme" parent="ThemeOverlay.AppCompat.Light">
<item name="colorAccent">@color/white_tint_1</item>
</style>
Apply it to the button like this
<android.support.v7.widget.AppCompatButton
android:id="@+id/item_reward_redeem_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/text_redeem"
android:textAppearance="@style/TextAppearance.AppCompat.Button"
android:textColor="@color/black_tint_3"
android:textSize="12sp"
style="@style/Widget.AppCompat.Button.Colored" //need this for press effect
android:theme="@style/RewardRedeemButtonTheme" //this will change the background
/>