Inspired by a case on this forum, I made this case for my students.
In 4 there is contact without damage

So, the quiz is Why did Red not protest?

I'm confused... is Red on starboard, as shown here, or (since the writing is backwards) is Red on port?

If Red is on starboard, then Blue needs to give Green room to duck Red, assuming Blue decides to duck, as opposed to tack (Rule 19.2.a-b). 

Assuming that's Red's on starboard, the next question is, Did Green have enough room? From your diagram, it looks like Green had about 1/6 a boatlength of gauge between themselves and Blue. To make that concrete, that's about 2.5 feet in a 14 foot Laser, and 4 feet in a J/24. That's a marginal amount of space for those two kinds of boats. 

In light air and flat water, Green could have probably gotten closer to Blue to avoid contact with Red; in this case, if on a protest committee, I'd penalize Green (Rule 10). In puffy and/or windy conditions, Green would need more gauge to safely pass to leeward of Red without hitting Blue, especially if they're pumping their main aggressively to depower; in that case, penalize Blue (Rule 19).

In other kinds of boats, e.g., full keel boats that don't turn quickly, 1/6 of a boatlength is probably not enough room. 

A question for the rules experts here: suppose Blue is vigilantly giving Green enough gauge to avoid contact between Blue and Green, but Green misjudges the duck, and due to Green's own bad driving, hits Red. Green can blame (and protest) Blue, even though the root cause Green negligence? Seems like Green gets a "get out of jail free" card here. What can Blue do here to strengthen their case? Can they hail to effect of, "Tell if me you need more room?" (Yes, I know a hail isn't required in a duck under 19.2.b; this is about proactively establishing facts if the situation goes into the protest room.)

Red did not protest as blue and green are protesting eachother and no damage done. Either green wins that and then he is mitigated or blue wins it and green is penalised anyway. Green has borne down without asking for water so as an aside to the question I would say that Green is in the wrong and will lose the protest.

I think red didn't ɟƨɘɟoɿᑫ because she found it too hard to pronounce

Green is neither entitled nor required by any rule to "ask for water."
Blue is required to provide room for Green to pass on the same side of Red that Blue does.
Red would be a fool not to hail "Protest" following a collision. And she is "expected to enforce" RRS 14..

What do you think about Blue breaks rule 19.....?

Facts found:

Conclusions:

Consequences

Catalan, it all comes down to whether there is enough space in the given conditions for the boats involved. It's certainly close, but it might still be enough room, depending on the types of boats and the conditions.

Nick, and other decision writers,

May I suggest you review the conclusions you have written, and rewrite them, by following the link to WS Preferred Standard Wording 2021-2024.

Then, go back and edit your Facts Found to delete irrelevant facts.

You could post your new decision here for us to have a look at.

Catalan,

Did your students fail if they didn't immediately refer to Case 11?