Amanda is fascinated to learn that aristocrats of this country rubbed a tinted mix-ture of gum arabic, gelatin, beeswax, and egg whites onto their nails to color them crimson or ebony, and in the 1100's punished commoners caught wearing a royal nail color by putting them to death. this behavior was common to the

I believe the answer is: Chinese

In the 1100's , the chinese use nail colour as a social symbol which distinguish their affiliation with nobilities. (higher status people which are close to the royal house tend to paint their nails with gold or silver color) . Common People who use a same nail color as the nobles would be Arrested due to the falsification of their status.