The Arduino microcontroller is currently one of the favorite tools of makers, and many teachers have used it in teaching or experiments. In addition, light-emitting diode (LED) smart lighting is the worldwide trend in lighting. There are many teaching demonstrations or applications of color addition using LEDs. Furthermore, the Internet of Things (IoT) is a popular emerging technology today, and the sensor is the most important component in the perception layer of the IoT, which makes teaching, research, or application related to sensors very important. Therefore, this study shows that an Arduino microcontroller can be used as an experimental setup for the teaching of light color mixing, light intensity detection, and ambient temperature sensing via a tricolor (red, green, and blue [RGB]) LED and two types of sensors: photoresistors and thermistors. The setup has intuitive, concrete, and multifunctional features, and is expandable, which is different from the typical experimental setup designed for only a single specific purpose. It is also suitable for students learning about light color mixing and sensor-related physics course experiments or demonstrations, whether they be in high school or college.