Electro-mechanical displays
This type of display utilizes the technology used in 7-segment displays. The display element used is a small plate on which the corresponding colour is applied, and it is controlled by an electromagnet or the movement of a miniature electric motor. Depending on the required display, the plate is tilted either with the colored side to show the segment or with the non-colored side, which serves as the background colour, to hide the segment.
This type of display is commonly used in platform clocks, airport halls, and similar places.