Hi everyone,
Can this sensor use to sense a line with 3 different color(Red, Green, Blue)?
I want to build a Arduino line following robot that capable of following a line other than black or white color.
Hello.
There are a few other posts that talk about using these QTR sensors on different colored surfaces. For example, this post by Grant answers a question about how well they would recognize different colors. Basically, our QTR sensors are not specifically intended to differentiate between mutli-colored surfaces, and how well they can do so will depend on the IR reflectivity of each surface. You would have to test it to see how the sensor responds to the different colors and find out if they would work for your application.
By the way, I noticed you asked the same question in a different thread. Since this question will be addressed here, we deleted the other post.
-Brandon
Thanks for reply 
Should I get Analog or Digital sensor? Do I need additional device or cable to read the value sensed by the sensor other than arduino UNO and USB cable?
Is the sensor capable of continuously detect different surface colors and perform the required action to allow the robot to move forward within the line? Or it only can sense 2 color like white line over black background for example at a time?
We generally recommend the digital versions of our QTR reflectance sensors. You can find more information describing the benefits of using this one from my post in this thread.
Aside from wires to connect and power the sensor array from the Arduino, you should be able to read the sensors using just the Arduino Uno and a USB cable for power.
You should not expect the QTR sensor to be able to accurately differentiate between colors; as I said before, the response of the sensors will be determined by the IR reflectivity of the surfaces, and it is not easy to predict what a red, blue, or green object will look like in IR (the reason they can differentiate black and white well is that black absorbs a wide spectrum of wavelengths and white reflects a wide spectrum wavelengths).
If you want to follow a solid white or black line, our QTR sensors are a good choice, but they are not appropriate for differentiating colors and are generally not good for following colored lines. For detecting colors, you might consider something like the ColorPAL.
-Brandon