2 LED Parallel circuit help?

Question

I need to make a circuit with 2 leds, 1 green 1 red.

If the current flows, green led will light up, if there is a break in the circuit (open circuit) it will light up another led as red. I don't know how to add the red led and make it light up when both switches in parallel are off. I have no clue how to do this without using a 3rd switch that says close if both switches are open. Help? I've heard of mosfets and spdt but I don't understand them. If someone could draw a beginner schematic it would be great.

Answer 1

^{simulate this circuit – Schematic created using CircuitLab}

The red led has 1.4V forward voltage drop while the green one has 2.2V. When the red one is on, the green one will not have enough voltage drop and will be very dim.

^{simulate this circuit}

If you want to turn off the green led completely off, you can use a MOSFET switch like this.

Answer 2

When S1 is made, current flows through K1's coil, pulling the armature down and connecting the Common contact to the Normally Open contact. That will allow current to flow through the green LED and its ballast resistor, lighting the LED.

When S1 is opened, current will no longer flow through K1's coil, the armature's spring will force the Common contact away from the Normally Open contact and connect it to the Normally Closed contact, lighting the red LED.