int ledPin = 23; 		// the number of the LED pin 
int ledState = LOW; 	// ledState used to set the LED 
long previousMillis = 0; 	// will store last time LED 
int interval = 1000;	// interval at which to blink (milliseconds) 

int ledPinG = 18; 		// the number of the LED pin 
int ledStateG = LOW; 	// ledState used to set the LED 
long previousMillisG = 0; 	// will store last time LED 
int intervalG = 500;

int ledPinY = 19; 		// the number of the LED pin 
int ledStateY = LOW; 	// ledState used to set the LED 
long previousMillisY = 0; 	// will store last time LED 
int intervalY = 2000;

void setup() 
{ 
pinMode(ledPin, OUTPUT); 
pinMode(ledPinG, OUTPUT);
pinMode(ledPinY, OUTPUT);
} 

void loop() 
{ 
// check to see if it's time to blink the LED; that is, if the difference 
// between the current time and last time you blinked the LED is bigger than 
// the interval at which you want to blink the LED. 
long currentMillis = millis(); 
if ( currentMillis - previousMillis >= interval) //currentMillis remains the same as 
//you are checking from the same clock
{ 
previousMillis = currentMillis; // save the last time you blinked the LED 
 	if (ledState == LOW)
 	{ 
ledState = HIGH;
 	}
else 
{ 
ledState = LOW; 
} 
digitalWrite(ledPin, ledState); 
}

if ( currentMillis - previousMillisG >= intervalG) 
{ 
previousMillisG = currentMillis; // save the last time you blinked the LED 
 	if (ledStateG == LOW)
 	{ 
ledStateG = HIGH;
 	}
else 
{ 
ledStateG = LOW; 
} 
digitalWrite(ledPinG, ledStateG); 
}

if ( currentMillis - previousMillisY >= intervalY) 
{ 
previousMillisY = currentMillis; // save the last time you blinked the LED 
 	if (ledStateY == LOW)
 	{ 
ledStateY = HIGH;
 	}
else 
{ 
ledStateY = LOW; 
} 
digitalWrite(ledPinY, ledStateY); 
}
}