It is used to describe that beauty is despised with the growth of years, just like a white pearl loses its luster in the passage of years.

Explanation 2. The word "Zhu" in "Old Pearl Yellow" stands for eyeball.

In fact, it is an abnormal phenomenon of eye metabolism. There is a thin transparent film on the surface of human eyeball, which is called conjunctiva. After being polluted by ultraviolet rays and dust for a long time, there will be adverse reactions of pigmentation.

Pigments gather in the conjunctival layer to form a large area of macula. A slightly raised dark yellow substance appeared on the surface of white eyeball, and the black eyeball became more turbid. Human beings have been stimulated by the external environment for a long time, and the elderly are more likely to produce conjunctival pigmentation, so there is a saying that "people are old and yellow."

Extended data

First, the source: Ming Lanling Xiao Xiaosheng's "Jin Ping Mei Hua Ci" for the second time: "My wife is young and has many days to turn over, unlike me, who is old and worthless."

Interpretation: Miss is still young, and the days ahead are still long. Unlike me, no one wants her when she is old.

Second, when people get old, the amount of garbage in our blood increases, and our transportation ability becomes worse. If we can't metabolize this garbage in time, our eyes will naturally turn yellow. The yellow here is the garbage in the blood. When people are old and yellow, it is difficult to look energetic. If you want to grow old, you must start from an early age and learn the way of keeping in good health.

References:

Baidu encyclopedia-people are old and yellow