Since the Toolbar is like any other view, you can change the way you want your text to look like particularly the title text:
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme.PopupOverlay">
<TextView
android:id="@+id/custom_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="16sp"
android:textColor="@color/colorRed"
android:text="@string/title_activity_mainr"/>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
This should help change the text color.
In fact, you can change the position of the title text as you wish!
Happy coding!