You can change color of underline (before - after - editing text) in EnterTextView.java:
This code:
- before: colorPrimaryDark
- after: colorPrimary
- editing: colorAccent
You can define number of underline by android:maxLength
<com.example.admin.canvascustomview.EnterTextView
android:layout_width="match_parent"
android:layout_height="72dp"
android:layout_gravity="center"
android:layout_marginBottom="24dp"
android:layout_marginLeft="72dp"
android:layout_marginRight="72dp"
android:layout_marginTop="20dp"
android:maxLength="4"
android:textSize="36sp"/>