Modification to plan mode is public or private

Hi,

I've added a few columns and color code to some of the default plan modes. Is this change public (which will affect other users' view on the plan) or private (which only myself can see the new column and the color)?

If it is "public"...
How can we prevent other users from modifying the public view of the plan?
How can we save a private view of the plan? Everyone want to view things in different way?

If it is "private"...
How can we modify the public view? I need to create a new plan mode, then associate with the plan?

Thanks,
Alice