Arduino LDR sensor stained
I've read you post a couple of times and I get the impression you would like this board to work, so here are some quick check to try and find the fault.  


You need a bread board
An arduino
A 200-300 ohm resistor.
Some wires. About 6 hands :)


Connect the board ground to the breadboard.  Then connect the to the resistor.  Then connect that to the power supply ground.

Take the positive off the power supply and touch it to the LED1 pin and check LED1 lights up.  Repeat with 2 and 3.

Switch every thing off

Connect the Positive to the Vcc connection of the board.
Connect a wire between Arduino A0 and "Sinal Analog"

Load this sketch

   void setup() {
       Serial.begin(9600);
    }
   void loop() {
       Serial.println(analogRead(A0));
       delay(250);
   }


When you cover the LDR it should read a lower number when you shine a light on it should read a higher number.

Turn everything off again, and if you have a multi meter test the resistance of the resistor on the board it should be 300 ohms, but I can't remember which way to read the bands and it might be 10K ohms, which would be a problem.

If anything doesn't work then they can all be fixed for a few cents and you don't need to worry about the discolouration.

Hope that helps you.