ARDUINO UNO LED + SWITCH

The code for that is really simple so you should be able to figure out what you need.  Here's a link to something that shows an led being lit when a button is pressed: you can extrapolate from that to what you need in terms of turning an led on or off.  Arduino function: delay(3000) will pause execution for 3 seconds (3000 milliseconds).  So you could turn an LED on, delay for 3 seconds, then turn it off.

You will have to decide what you mean by "if the switch is not pressed" because of course the majority of the time it won't be pressed, so how often do you want to light the green LED when it detects the button not pressed. 

The link has code that shows you how to detect if a button is pressed or not pressed and how to turn on and turn off an LED.  It also has pictures on how to wire up the button and LED - for your second LED do the same but with a different digital port, e.g. 4.  You don't need to use more than one breadboard if you don't want to as long as you make sure your wiring is correct.

Just use a flag to keep track if the process is done or not.

When you detect a change from press to not press or from no press to press activate the flag

setup(){
     set lastButtonState to pressed;
     set processedFlag to false;
}
loop(){
  read newButtonState;
  if lastButtonState is not equal to newButtonState and processedFlag is false  then { 
    if(lastButtonState is pressed) {
      turn on red led;
      wait for 3 seconds;
      turn off red led;
    else {
      turn on green led;
      wait for 3 seconds;
      turn off green led;
     }

     set processedFlag to true;

  } else{
    set processedFlag to false;
  }
  set lastButtonState to newButtonState;
  delay some time for debouncing button
}

if the leds are on during 3 seconds you can skip the debouncing delay