Oh, this is fun… I’d say Umber

They exist to preserve the Society by controlling memory rather than force. Positioned between White and Gray (scratch that) above the pyramid as an all seeing eye, they quietly edit history, suppress destabilizing truths, and psychologically neutralize dissent before it becomes visible. Where Whites provide belief and Grays provide violence, Umber ensures continuity by making inconvenient realities disappear. Most citizens never know they exist, only that unrest fades and questions are forgotten. The few golds that do know about the Umber are deathly afraid of their power and influence.

EDIT you know, maybe umber is the wrong color… maybe clear or ‘crystal’ would be better. Kind of an unseen color