Temperature-controlled RGB LED

#define TEMP_PIN A0
#define RED_PIN 9
#define GREEN_PIN 10
#define BLUE_PIN 11

int adc = 0;
int blue = 0, red = 0;

double ReadThermistor(int adc) {

  double resistance = ((1024.0/adc) - 1);    //calculate from voltage divider, for 10k resistor
  double Temp = log(resistance);

  // calculate the temperature, in K, using 4 thermistor model/material specific parameters A, B, C, D
  // here we use the values for the Sparkfun/Hactronics version of the Vishay 10k NTC thermistor
  Temp = 1 / (0.003354016 + 0.0002569850 * Temp + 0.000002620131 * Temp * Temp + 0.00000006383091 * Temp * Temp * Temp);
  Temp = Temp - 273.15;            // Convert Kelvin to Celsius
  return Temp;
}

void setLED(int blue, int red){
  analogWrite(BLUE_PIN, blue);
  analogWrite(RED_PIN, red);
}

void setup(){
  Serial.begin(9600);
  pinMode(BLUE_PIN, OUTPUT); 
  pinMode(RED_PIN, OUTPUT); 
  pinMode(GREEN_PIN, OUTPUT);  
  pinMode(TEMP_PIN, INPUT);
}

void loop(){
  adc = analogRead(TEMP_PIN);
  int temp = ReadThermistor(adc);
  Serial.println(temp);
  
  red = map(temp, 20, 40, 0, 255);
  blue = 255 - red;
  
  setLED(blue, red);
}