When you need to quantify the color of an object ... or you can buy an off-the-shelf RGB sensor and wire it up to an Arduino. Or you can go back to basics and build this reflective RGB sensor ...

[Jordan’s] sensor includes just a single pixel. The sensor is really just an infrared photodiode inside of a tube. The diode is connected to an analog input pin on an Arduino. The sensor can be ...

Here is a list of projects ... Arduino is able to interpret signals from a variety of sensors. By placing a unit equipped with an ADXL345, an accelerometer for detecting motion, or a Piezo sensor ...