Grays are a lower tier caste. They serve as the police and military personnel of society, and keep the lower Colors in line. Many are shown to be abusive to lowColors beneath them. Their name identifier is ti, the chemical symbol for Titanium.
Lurchers
While most Grays will not be able to attain a high rank, these Grays are trained for killing Golds. Named so after the mutts on Earth, which were crossbred to take down preys larger than they are.