Can you solve it? The puzzle of the red and green hats

Hi guzzlers,

A box contains two red hats and three green hats...

You may recognise this opener as the start of a famous puzzle - whose origins date back to the 1940s - about three logicians who close their eyes and randomly take out a hat from the box and put it on. With their eyes open they must deduce the colour they are wearing based on the hats they can see on the others.

Today’s puzzle is a new version with a witty twist: one of the logicians is colourblind!

A box contains two red hats and three green hats. Azalea, Barnaby and Caleb close their eyes, take a hat from the box and put it on. When they open their eyes they can see each other’s hats but not their own. They do not know which hats are left in the box.



We can assume that all the protagonists are perfect logicians who tell the truth. They know all the information in the above paragraph. In addition, one of them is colourblind. They all know who the colourblind person is.

Azalea says: “I don’t know the colour of my hat.”



Barnaby says: “I don’t know the colour of my hat.”



Caleb says: “I don’t know the colour of my hat.”



Azalea says: “I don’t know the colour of my hat.”



Who is the colourblind person, and what colour is their hat?



The puzzle was designed by the American puzzle enthusiast Jack Lance, and he thought it up because one of his friends on a puzzle forum is colourblind.

I’ll post the solution at 5pm today.

UPDATE: The solution can now be read here.

Meanwhile, NO SPOILERS! Please talk about hats, or suggest other interesting variations of the classic puzzle.

I set a puzzle here every two weeks on a Monday. I’m always on the look-out for great puzzles. If you would like to suggest one, email me.

If you like logic problems like this one, there are several more in my puzzle book Can You Solve My Problems?