Red Rising by Pierce Brown

Darrow is a Red, a member of the lowest caste in the color-coded society of the future. Like his fellow Reds, he works all day, believing that he and his people are making the surface of Mars livable for future generations.

Yet he spends his life willingly, knowing that his blood and sweat will one day result in a better world for his children.

But Darrow and his kind have been betrayed. Soon he discovers that humanity already reached the surface generations ago. Vast cities and sprawling parks spread across the planet. Darrow—and Reds like him—are nothing more than slaves to a decadent ruling class.