Earlier, we explained that the team must save certain types of cards with Save Clues.
But above and beyond this, we also agree that we must "get" all of the playable cards. In order words, we don't let each other discard playable cards!
So, the full list of what we must not discard is the following:
Unique 2's (i.e. 2's that are the only copy currently visible)
Critical cards (i.e. cards that have all other copies discarded)
Unique playable cards (i.e. playable cards that are the only copy currently visible)
Not letting each other discard important cards is called Save Principle and it is the most important principle of them all. You are allowed to break any other principle or rule in order to prevent a card in this list from being discarded. In fact, sometimes you will have to violate Good Touch Principle in order to save a specific card, and that is okay.
Alice needs to save the final blue 3 on Bob's chop.
Alice knows that she is allowed to perform Critical Saves with either a color clue or a number clue.
If Alice clues blue, it will violate Good Touch Principle because it will also touch both copies of blue 4.
If Alice clues number 3, it will violate Good Touch Principle because it will touch the red 3 (and the red 3 is already played on the stacks).
Here, Alice knows that it is better to violate Good Touch Principle than to lose the chance at a perfect score. Thus, Alice must choose between the lesser of two evils and decide between cluing blue and cluing number 3.
Alice decides to clue blue to Bob instead of number 3 because at least one of the blue 4's will be useful later on.