I tried to examine the relationship between the measurement result and the distance between the color sensor and the object. When you run "View" in the state of the photo above, you will see the "5.Red" of course. In this state, I'll take one potch block away from the sensor.

Around the distance of the sensor has reached 28mm, "Red" become "Black" on the display or the results were unstable,.

Sometimes a small change in the environment, the measurement result would be changed.
For example, put closer the light of fluorescent lamps "Red" has become "Black" was displayed.

It went back in "Red" if you around the sensor by hands. This could be caused by a non-LED light, so the sensor is becoming unstable.