This bidirectional circuit was found in an American documentation from the 80's. The LEDs are common red, and the resistor is calculated according to the formulas next to the diagram.
For those who like experimental circuits, here is a sequential flasher system with LEDs, which can be...
This circuit is from an Electronics Now from the 90s. Operational amplifiers can be replaced by...
This circuit is from a Hughes documentation from 1968. The components are of the time and the RC...