The circuit uses independent timers to flash two light emitting diodes. Any time that light emitting diode D1 is lit__light emitting diode D2 will be switched off. Light emitting diode D3 is on if both D1 and D2 are off.
Two versions of the circuit are shown. The second circuit uses fewer components by taking advantage of the bipolar outputs of the timers.
If the supply voltage is increased a 1N4148 diode should be placed in series with light emitting diode D3. The values of the resistors should also be increased proportionately.