Updated to add a cancellation button and prevent hanging when closing the window opened by the ellipses menu item via the X in the upper right corner. Now that will also cancel the operation. Improved default colour choosing in the dialog (matches the behaviour of the non-dialog version now for its default colour) and gave the window a more appropriate title.
As before, the 2013 version is backsaved and untested. Only the 2017 version is tested.