A joke, I don't understand.

Well, Dalton is color blind! Can't tell red from blue, please see the following story:

When Christmas came, Dalton gave his mother a pair of socks as a gift to show filial piety.

"John!" After seeing these socks, my mother was unhappy and shouted angrily, "How can you buy a pair of red socks!" " "

According to local religious customs, women are forbidden to use red. But what Dalton bought was blue. He looked at it again. Yes, it is blue.

"Mom, this is a pair of blue socks."

"What?" Mother looked at Dalton in surprise. "Son, you won't get dizzy, will you?"

Dalton was very surprised. He showed his socks to others. Sure enough, they said it was red. Dalton couldn't help being blindsided.

Suddenly, he remembered that when he was a child, he and his younger brother Jonadan had smoked a gyro together. It's a red top, but Jonadan insists it's green. Another time, his sister wore a new green dress, but Qiao Dandan said it was red. Do he and his brother have visual defects?

The scientist opened his mind.

After a detailed study, Dalton experimented with squares of various colors among primary school students. He found that some students can't tell colors at all, and some often misread various colors. They regard green as red, or red as green, and some can't tell blue from yellow.

1794 Dalton wrote a report about color blindness, pointing out that color blindness exists in human beings. Dalton's discovery attracted public attention, so in Britain, people called color blindness Dalton's disease.