How is skin color important in the book?

According to the novel, the color of someone's skin is very important in Mexican society. A few shades can determine how a person will be treated throughout life. If they are lighter, then the luck of society will follow that person, if darker, then he or she must prove they are better than the color of their skin. People always want to marry higher up in class; thus, they aim for someone lighter than they to better the race.