Colors of Madness

You create a twisting pattern of colors unknown to natives of the material plane.  These eldritch colors weave through the air inside a 30-foot cube within range. The pattern appears for a moment and vanishes. Each creature in the area who sees the pattern must make a Wisdom saving throw. On a failed save, the creature becomes insane (roll on Short-Term Madness table, DMG p. 249) for the duration. 

The spell ends for an affected creature if it takes any damage or if someone else uses an action to shake the creature out of its madness.