Color Sensors

What is a Color Sensor?

A color sensor measures the amount of red, green, and blue light reflected from an object. By comparing these values against predefined thresholds, your robot can determine what color an object is.

Most color sensors also report an alpha value, which represents the overall light intensity reflected back to the sensor.

FTC teams commonly use the REV Color Sensor V3, which also includes a short-range distance sensor.

Common Uses

• Detecting game piece colors
• Determining if a game piece is present
• Line following
• Autonomous decision making
• Sorting game pieces

Initializing a Color Sensor

First, retrieve the sensor from the hardware map.

ColorSensor colorSensor;

colorSensor = hardwareMap.get(ColorSensor.class, "color_sensor");

Enabling the LED

Always enable the sensor's built-in LED before reading color values. The LED provides consistent lighting and helps reduce inaccuracies caused by changing ambient light.

colorSensor.enableLed(true);

Reading Color Values

A color sensor returns four values ranging from 0 to 255.

int red = colorSensor.red();
int green = colorSensor.green();
int blue = colorSensor.blue();
int alpha = colorSensor.alpha();

Reading an ARGB Value

You can also retrieve a single packed ARGB color value.

int argb = colorSensor.argb();

This combines the alpha, red, green, and blue values into one integer.

Using the REV Color Sensor V3

The REV Color Sensor V3 includes all of the standard color sensing features while also providing a built-in short-range distance sensor.

Initialize it using the RevColorSensorV3 class.

RevColorSensorV3 colorSensorV3 =
        (RevColorSensorV3) hardwareMap.colorSensor.get("colorV3");

Reading Distance

The V3 sensor can detect whether an object is directly in front of it.

double distance = colorSensorV3.getDistance(DistanceUnit.CM);

The distance sensor is effective from approximately 1 cm to 10 cm.

NOTE: The V3's distance sensor is best used to determine whether an object is present, not to accurately measure the distance between your robot and field elements. For longer-range measurements, use a dedicated Time of Flight distance sensor.

Color Thresholding

Instead of checking for exact color values, compare the readings against thresholds.

if (colorSensor.red() > 150 && colorSensor.blue() < 80) {
    telemetry.addLine("Red Object");
}

Thresholds should be determined by testing with your actual game pieces under the lighting conditions used during competition.

Best Practices

• Enable the LED before taking readings.
• Mount the sensor close to the object being detected.
• Use thresholds instead of exact values.
• Test under different lighting conditions.
• If using the REV Color Sensor V3, use its distance sensor to detect object presence rather than precise distance.