Final answer:
In the 'Red Rising' series by Pierce Brown, The Sons of Ares are blamed for a terror attack on Red and Orange.
Step-by-step explanation:
The group blamed for a terror attack on Red and Orange is a) The Sons of Ares. The Sons of Ares are a rebellious group depicted in the fictional universe of the 'Red Rising' series by Pierce Brown. The series is set on a future Mars, where society is divided into color-coded castes. The Sons of Ares is an underground movement fighting against the oppression by the higher castes, especially the Golds, who rule over the others. The reference to Red and Orange pertains to the colors of the society tiers that were targeted in the story.