Software apps and online services
My student and I built an interactive RGB lamp.
You can change the color of the lamp by placing a syringe with colored water into desired position. For each color we use one syringe (red, green, blue). Plunger of the first syringe moves the plunger of the second syringe, and it moves a linear potentiometer. Therefore, the voltages are changed to three analog inputs of arduino.
You can take a lampshade with some old lamps or make it from the sturdy wire and transparent material.