WordPress/src/main/res/drawable/nux_flat_button_grey_text_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="@color/grey_lighten_30" android:state_pressed="true" />
    <item android:color="@color/nux_grey_button" />
</selector>