One would not think trying to arrange 4 cubes so that each of the 4 colors appear on the top, bottom, front and back, once and only once. This has been a popular puzzle ever since first appearing in 1968, as over 20 million have been sold, claims Willing Moves Games. I don’t know if that number is only those sold by them, as I have had one by Parker Brothers for many years. I also have a couple of wooden sets that come with a wood case with a chord to keep the cubes secure. It is very well made of exotic wood and made in Thailand by Mandalay. That one goes by the name Color Cubes. It gives the same puzzle to solve (each color once and only once on the top, bottom, back and front).
However, it gives two other Puzzles;
Puzzle 2. Arrange the cubes in a square so that there are 4 different colors on top, 4 different colors on the bottom, and only 1 Color on each side.
Puzzle 3. Arrange the cubes in a square so that there are 4 colors on top,4 different colors on the bottom and only 1 color on each side.
Solutions for the 3 Puzzles are provided in the Mandalay version.
This set does not come with a solution, but directs you to their Website,or YouTube where you will find excellent videos explaining how to go about solving the puzzle.
As to difficulty, this would be extremely difficult to solve by chance.However with a method , as found on YouTube, it is possible.
You can purchase this puzzle and get the solution at Puzzle Master.