In Anthem, why does Equality 7-2521 begin to notice color in the world the first time he sees Liberty 5-3000?

a. commuting the transgression of "taking notice" of Liberty 5-3000 allows him to begin to take notice of the world around him

b. he had never seen anything else in the city with colors, as everything is dark and gloomy.

c. Equality 7-2521 was born with a color blindness that goes away when he is in fields and forests.

d. She shows him colors and explains them to him through words and gestures.