For Arduino

sketch.ino

int rgbR = A0;
int rgbG = A1;
int rgbB = A2;
int mapR=0;
int mapG=0;
int mapB=0;
int r=0;
int g=0;
int b=0;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  r = analogRead(rgbR);
  g = analogRead(rgbG);
  b = analogRead(rgbB);
  mapR = map(r,0,1023,0,255);
  mapG = map(g,0,1023,0,255);
  mapB = map(b,0,1023,0,255);
  
  //Serial.print("R :");
  //Serial.print(mapR);
  //Serial.print(" G :");
  //Serial.print(mapG);
  //Serial.print(" B :");
  //Serial.println(mapB);
  Serial.print(mapR);
  Serial.print(",");
  Serial.print(mapG);
  Serial.print(",");
  Serial.println(mapB);
  delay(100);
}