The “two flashing led” circuit is designed for 9 Volts but it works at lower voltages too. In this design we used red leds but by changing the series resistors R1 and R4 you can also use different LED ...

Resistor R2 makes the LED current to a safer value of 30 mA. When the diac conducts, C1 discharges and again the breakdown voltage of diac decreases and LED turns off. Thus the charging/discharging ...