Color Quadrants

Color Quadrants

Colors are defined with specific X,Y coordinates, but normal people use terms like "green" or "blue" to describe a color.

However, how do we make sure "blue" is the same, and not "red-blue" or teal in color?

SAE has defined quadrants, or areas on the chart, for each major color of automotive lights. The color of a lights must fall into the correct color quadrant to be legal for on-road use. 

For example, all brake lights must emit a color that falls inside the Red color quadrant. A small quadrant exists for Selective Yellow, used for fog lamps.

Notice how long the White quadrant is, which is used for headlamps.. That large area is what allows us have both warm white halogen headlights, and cool white LED headlights, both legal for use on the road.

To see if a color is correct, we plot the measured value on this chart, with X, Y coordinates, and make sure it falls within the quadrants. This is what technically determines if the color is "correct" or not.