Злобный Ящур
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Out of 4, only 3 can be saved because, based on the first person's answer, 2 won't be able to distinguish between "red, red, red" and "blue, red, red". So, unfortunately, 3 out of 2 is the maximum.
The first person looks at 2, 3, and 4.
If all 3 colors are the same, they name that color. If 3 and 4 have the same color, and 2 is different, they name the remaining color (which none of the other 3 have). If all 3 are different, they name the color of the second person. If 2 and 4 have the same color, and 3 is different, they name the color of the third person. If 2 and 3 have the same color, and 4 is different, they name the color of the fourth person.
The second person listens to the first person's answer and looks at the remaining ones.
If 3 and 4 have colors that match the first person's answer, they repeat the answer. If 3 and 4 have the same color, but it's different from the first person's answer, they name the remaining color. If 3 and 4 have different colors and they are different from the first person's answer, they repeat the first person's answer. If 3 and 4 have different colors and one of them matches the first person's answer, they name the other color.
The third person listens to the first two answers and looks at 4.
If the first and second answers match the color of 4, they repeat the answer. If the first and second answers match, but are different from the color of 4, they name the remaining color. If the first and second answers are different and they are different from the color of 4, they name the color of 4. If the first and second answers are different and one of them matches 4, they name the other color.
The fourth person listens to the first three answers.
If all 3 answers are the same, they repeat the answer. If the first and second answers match, but are different from the third answer, they name the remaining color. If all 3 answers are different, they repeat the third answer. If 2 answers are the same (except for the case where 1 and 2 are the same!), and the third is different, they repeat the answer that is different.
2, 3, and 4 are 100% safe! Probably...
Added 7 minutes later
I have a feeling that the answer is that all but one can be saved, and that one has a chance to be saved.
Ничто не возникает из ничего и ничто не пропадает бесследно.
Если где-то чего-то убудет, то в другом месте добавится.
(Закон сохранения).