The most common triad are mixing the primary colors: red, blue, and yellow. The resulting colors depends on which primary colors one mixes. Ultramarine blue, phthalo blue, and cobalt blue mixed with Cadmium Yellow light will result three different greens.
An interesting triad are mixing the secondary colors: Orange, Green, and Purple.
Cadmium and Pyrrole Orange, Ultramarine Violet, and Yellow Green
