session-android/res/drawable/progress_button_state.xml

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