Color Purity is a measurement of monitor quality. It is measured by displaying pure screens of red, blue and green and matching the actual color displayed at (five) different locations on the screen to a "Chromaticity chart" which shows colors as a function of hue and saturation. The metric is a "Gap Score" which shows how much the observed colors differ at the five different points in terms of distances on the chromaticity chart. Good scores are around 20. Poor scores may exceed 100.

As a practical test, one could also check the display with a magnifying glass. When displaying one pure color, pixels of other colors should not be lit at all. It would be difficult to quantify these results.

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