Color sensors register items by contrast, true color, or translucent index. True color sensors are based on one of the color models, most commonly the RGB model (red, green, blue). A large percentage of the visible spectrum can be created using these three primary colors.

Many color sensors are able to detect more than one color for multiple color sorting applications.  Depending on the sophistication of the sensor, it can be programmed to recognize only one color, or multiple color types or shades for sorting operations.

Some types of color sensors do not recognize colors, per se, instead focusing on light wavelengths.  These devices can be configured to locate wavelengths from near infrared (colors in the 750 nm to 2500 nm wavelength range), far infrared (colors in the 6.00 to 15.00 micron wavelength range), and UV (colors in the 50 to 350 and 400 nm wavelength range), in addition to the visible range.  Sensors that read the visible range are the most common type of color sensors. They measure color based on an RGB color model (red, green, blue). A large percentage of the visible spectrum (380 nm to 750 nm wavelength) can be created using these three colors.

Color sensors are generally used for two specific applications, true color recognition and color mark detection.  Sensors used for true color recognition are required to "see" different colors or to distinguish between shades of a specific color. They can be used in either a sorting or matching mode. In sorting mode, output is activated when the object to be identified is close to the set color. In matching mode, output is activated when the object to be detected is identical (within tolerance) to the color stored in memory.  Color mark detection sensors do not detect the color of the mark, rather they "see" differences or changes in the mark in contrast with other marks or backgrounds. They are sometimes referred to as contrast sensors.

Color sensors shine light onto the object to be monitored and measure either the direct reflection or the output into color components. Many color sensors have integral light sources to achieve the desired effect.  These integral light sources include LEDs, lasers, fiber optic, and halogen lamps.