While Funtion

const int RedPin= 9;
const int BluePin= 11;
const int GreenPin= 10;
unsigned long timeVal=0;
int maxVal=0;
int minVal= 1025;
const int PhotoPin=A0;
int PhotoVal=0;

void setup()
{
pinMode (RedPin, OUTPUT);
pinMode (BluePin, OUTPUT);
pinMode (GreenPin, OUTPUT);
Serial.begin(9600);
digitalWrite (BluePin, HIGH);
timeVal=millis();
while (millis()-timeVal<5000)
{
PhotoVal= analogRead(PhotoPin);
if (PhotoVal>maxVal)
{
 minVal=PhotoVal;
}
    if (PhotoVal>maxVal)
    {
      minVal=PhotoVal;
    }
}
digitalWrite(BluePin, LOW);
Serial.print ("minVal=");
Serial.print(minVal);
Serial.print(" maxVal=");
Serial.println(maxVal);
}
void loop()
{
PhotoVal=analogRead(PhotoPin);
PhotoVal=map(PhotoVal, minVal, maxVal, 255,0);
PhotoVal=constrain(PhotoVal, 0,255);
analogWrite(BluePin,PhotoVal/2);
analogWrite(GreenPin,PhotoVal/4);
analogWrite(RedPin,PhotoVal/4);
}