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