int potPin = A3; 
int potVal = 0; 

int redPin = 9;   
int grnPin = 10;  
int bluPin = 11; 

int redVal = 0;  
int grnVal = 0;
int bluVal = 0;

void setup()
{
  pinMode(redPin, OUTPUT);   
  pinMode(grnPin, OUTPUT);   
  pinMode(bluPin, OUTPUT); 
}

void loop()
{
  potVal = analogRead(potPin);   
  if (potVal < 341)  

  {                  
    potVal = (potVal * 3) / 4; 


    redVal = 256 - potVal;  
    grnVal = potVal;        
    bluVal = 1;             
  }

  else if (potVal < 682) 
  {

    potVal = ( (potVal-341) * 3) / 4; 
    
    redVal = 1;           
    grnVal = 256 - potVal;
    bluVal = potVal;       
  }

  else  
  {
    potVal = ( (potVal-683) * 3) / 4;

    redVal = potVal;      
    grnVal = 1;           
    bluVal = 256 - potVal; 
  }

  analogWrite(redPin, redVal);   
  analogWrite(grnPin, grnVal); 
  analogWrite(bluPin, bluVal);  
}