Hi,

What does it mean when a WL book is highlighted in pink?

It's on hold.

This happens if you put it on hold yourself; if you use the Not Now feature when it's been offered to you; if you are offered another version of the book and accept.

You need to manually turn off the Hold if you want the wish to be active again.  Click the box next to the book, then go to the top of the page to select the action. 

The wish list has the box on one side, the bookshelf has the box on the opposite side.  One is right and one is left, but I can never remember which is which without looking. 

I believe that another reason could be you have accepted another version of the book, or is en route to you.  I have a paperback and hardcover version of the same book on my wishlist.  If the hardcover gets offered to me and I accept it, the paperback version on my wishlist often gets highlighted in pink and put on "hold".  Not sure if that's standard, or if it's something I have set up in my settings or not.

It only happens if the two versions are successfully linked.   Different versions do not always link.  A slight difference on the title or author name will prevent linking.   (Our computer thinks John H Smith and John H. Smith are two different authors.)

In other words, don't assume the other version will be put on Hold.