How do I hide or show all labels on a Trello board?

Question

How do I hide or show all labels on all cards at once?

A few times, it happened to me, that I hit a button which hides all labels from cards in Trello. I tap it again, and it hides all labels all together. Once more, and the label re-appears.

This time around, I did not notice which button I pushed - and now all my labels are not showing, when I look at the whole board.

It looks like this:

But I want it to look like this:

Answer 1

On my Macbook UK keyboard, I finally found the key to be the : / ; key, just to the right of L.