Color-mixing lamp on an Arduino Uno

// Color-mixing lamp: three light sensors, each behind a colored gel, set the
// red, green and blue of one RGB LED.
//
//   phototransistors   collector -> 5V, emitter -> A0 / A1 / A2, and a 10k
//                      resistor from each emitter to GND
//                      A0 behind the red gel, A1 green, A2 blue
//   RGB LED            red -> pin 10, green -> pin 9, blue -> pin 11, each
//                      through 220 ohm; the long leg (common cathode) to GND
//
// Each phototransistor passes more current the more light falls on it, and
// its 10k resistor turns that current into a voltage on the analog pin. The
// gel in front lets through mostly one color, so each sensor measures one
// part of the light around it, and the lamp copies that mix.
//
// analogRead gives 0 to 1023 and analogWrite takes 0 to 255, so each reading
// is divided by 4 on the way across.

const int RED_LED = 10;
const int GREEN_LED = 9;
const int BLUE_LED = 11;

void setup() {
  pinMode(RED_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(BLUE_LED, OUTPUT);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: color-mixing lamp");
}

void loop() {
  int red = analogRead(A0);
  delay(5);
  int green = analogRead(A1);
  delay(5);
  int blue = analogRead(A2);

  analogWrite(RED_LED, red / 4);
  analogWrite(GREEN_LED, green / 4);
  analogWrite(BLUE_LED, blue / 4);

  Serial.print("raw red ");
  Serial.print(red);
  Serial.print(", green ");
  Serial.print(green);
  Serial.print(", blue ");
  Serial.println(blue);
  delay(250);
}