On my watercolor discord, I joked that an “evil primary triad” would be Hansa Yellow Light, Pyrrol Red, and Ultramarine Blue. In most triads, you optimize for vibrance in one area while sacrificing it in another; in this triad, although the primary colors themselves are bright, all the secondaries – oranges, greens, and violets – would be muted and dull.
Of course everyone then got invested in proving me wrong and painting gorgeously with this (actually fairly traditional) triad.