Alice needs to give a Play Clue to Bob's blue 3 before it is discarded.
If Alice clues blue, then it would focus the blue 3, but the blue 2 would be duplicated (because it is already played on the stacks).
If Alice clues number 3, then it would focus the blue 3, but it would also touch the red 3. The red 3 is useful to the team in the future, so this is a good thing.