Hi GoghGirl,
You should be able to do all of that already

. This plugin does not care whether you have formats associated with a book or not. So you can use the "Add Empty Book" feature from the Add button menu in the calibre toolbar (or use ctrl+shift+e). Then grab metadata for that book as per normal.
Alternatively say you have a "wishlist" shelf in Goodreads that you maintain on their website. Then when you sync from that shelf you will be shown books on the shelf which you don't have a book in calibre for yet. You can right click and choose the add empty book option. I can't recall how many of the fields that option populates but you can always do a metadata download for that book afterwards.
As for the colouring, calibre has the ability to do custom colouring rules, so you could set up a rule for books in your library that have no formats. I am sure there will be information on this in the calibre help, plus there are threads here like
this one.
Have fun!