For setting default theme, I set that in application tag in the manifest file.
<application
android:name=".App"
android:icon="@drawable/icon"
android:label="@string/app_name"
android:theme="@style/AppTheme">
And this is the 'AppTheme' in styles.xml.
<style name="AppTheme" parent="Theme.AppCompat.NoActionBar">
<item name="android:textColor">#0400ff</item>
<item name="android:editTextColor">#ff0000</item>
</style>
This works in Android 5.0 and 6.0 devices. But in Android 4.x, oddly it works only for 'textColor' not 'editTextColor'. Although I set this theme, default editText color is white in android 4.x. I don't know why this problem happened. Please give me some hints!