Color Sensor Basics

The color sensor (most common being the REV Color/Range Sensor) allows your robot to detect colors, light levels, and even proximity. This is essential for detecting team props, game pieces, or tape on the field.

Tip

Why use a Color Sensor? Beyond just “seeing” color, these sensors are great for identifying the orientation of objects or ensuring a robot has correctly grabbed a specific game piece.

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Add the sensor to your hardware map using the NormalizedColorSensor class. This interface is recommended because it provides consistent values (0.0 to 1.0) regardless of the sensor’s internal resolution.

import com.qualcomm.robotcore.hardware.NormalizedColorSensor;
import com.qualcomm.robotcore.hardware.NormalizedRGBA;

NormalizedColorSensor colorSensor = hardwareMap.get(NormalizedColorSensor.class, "colorSensor");

Read the colors into a NormalizedRGBA object.

NormalizedRGBA colors = colorSensor.getNormalizedColors();

telemetry.addData("Red", "%.3f", colors.red);
telemetry.addData("Green", "%.3f", colors.green);
telemetry.addData("Blue", "%.3f", colors.blue);

3. Detecting Specific Colors

Comparing raw RGB values can be tricky because lighting conditions change. A common technique is to check which value is the highest.

if (red > blue && red > green) {
    telemetry.addData("Color", "Red Detected");
} else if (blue > red && blue > green) {
    telemetry.addData("Color", "Blue Detected");
}

For more reliable color detection, it’s recommended to convert your RGB values into HSV (Hue, Saturation, Value).

float hsvValues[] = {0F, 0F, 0F};
NormalizedRGBA colors = colorSensor.getNormalizedColors();
Color.colorToHSV(colors.toColor(), hsvValues);

telemetry.addData("Hue", hsvValues[0]);

Tip: Red is usually around 0 or 360, Blue is around 240, and Yellow is around 60.

5. Built-in Distance Sensing

Many color sensors (like the REV V3) also function as distance sensors. This is great for “Check if a piece is in the intake” logic.

import org.firstinspires.ftc.robotcore.external.navigation.DistanceUnit;

double distance = ((DistanceSensor) colorSensor).getDistance(DistanceUnit.CM);
telemetry.addData("Distance (cm)", "%.2f", distance);

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package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
import com.qualcomm.robotcore.hardware.NormalizedColorSensor;
import com.qualcomm.robotcore.hardware.NormalizedRGBA;
import com.qualcomm.robotcore.hardware.DistanceSensor;
import org.firstinspires.ftc.robotcore.external.navigation.DistanceUnit;
import android.graphics.Color;

@TeleOp(name = "Normalized Color Sensor Example", group = "Sensor")
public class ColorSensorExample extends LinearOpMode {

    private NormalizedColorSensor colorSensor;

    @Override
    public void runOpMode() {
        colorSensor = hardwareMap.get(NormalizedColorSensor.class, "colorSensor");

        telemetry.addData("Status", "Initialized");
        telemetry.update();

        waitForStart();

        while (opModeIsActive()) {
            // 1. Get normalized colors (0.0 to 1.0)
            NormalizedRGBA colors = colorSensor.getNormalizedColors();
            
            // 2. Convert to HSV
            float hsvValues[] = {0F, 0F, 0F};
            Color.colorToHSV(colors.toColor(), hsvValues);
            
            // 3. Read distance
            double dist = ((DistanceSensor) colorSensor).getDistance(DistanceUnit.CM);

            // 4. Detection Logic
            String detected = "NONE";
            if (dist < 5.0) {
                if (hsvValues[0] < 30 || hsvValues[0] > 330) {
                    detected = "RED";
                } else if (hsvValues[0] > 200 && hsvValues[0] < 260) {
                    detected = "BLUE";
                }
            }

            telemetry.addData("Object", detected);
            telemetry.addData("Hue", "%.1f", hsvValues[0]);
            telemetry.addData("Distance (cm)", "%.1f", dist);
            telemetry.update();
        }
    }
}

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Lighting: The REV Color Sensor has a built-in LED. You can turn it on or off using colorSensor.enableLed(true). This is helpful for surface detection but might interfere with detecting distant objects.