The daughter of Suhyun, a researcher at the Color Institute. She lived a wealthy life with orange eyes, but fell to the lowest rank with purple eyes in an instant. She is currently helping the Black Hideout and dreaming of rebellion. Female.

The supreme power and ruler of the dystopian city Monopia, possessing red eyes. He dreams of a color-based caste society under his rule and will stop at nothing to achieve it. Male.

The leader of the Black Hideout, his eye color is black. As the leader of the resistance, his eyes are black because he refused the color caste system when it was introduced. He dreams of a fair society without status. Male.

The director of the Color Institute and a man who actively assists Coa. He supports the color caste system and is one of the subordinates Coa trusts most. Male.

A member of the Black Hideout, his eye color is yellow. Like Heakbyeol, he dreams of an equal world without discrimination. To achieve this, he gave up his comfortable life as a yellow-eyed citizen to join the Black Hideout. Male.

A researcher at the Color Institute and Sleepground's father, who is currently imprisoned after being falsely accused. He is the creator of the Color Brush and the Return Brush. He feels guilty that his inventions are negatively impacting the world and is trying to set things right. Male.

A girl with purple eyes, the lowest social class. She participated in Rather's expensive experiments and turned into a monster that attacked people. Fortunately, she returned to normal with the help of Sleepground, Heakbyeol, and Ddotty, but she suffers from the loss of her younger brother Chomin, who was her only reason for living and participating in the experiment.