The Color Wheel's Secret

Isaac Newton created the first color wheel in 1704 by bending the straight spectrum into a circle. To close the circle, he connected red and violet with a segment that doesn't exist in the rainbow — the purple-magenta bridge.

A screen makes magenta the same way your brain does: it lights the red and blue pixels and leaves green dark. But this trick has a limit. Three fixed primaries can only blend the colors that fall inside the triangle they form — a screen's color gamut.