Three knobs mix an RGB LED (pins 11, 10 and 9), on an Arduino Uno

// Mix a color by hand: three knobs, one for each color of an RGB LED.
//
//   knob 1 -> A0 sets red on pin 11    knob 2 -> A1 sets green on pin 10
//   knob 3 -> A2 sets blue on pin 9    each knob's ends -> 5V and GND
//   RGB LED legs -> 220 ohm each -> pins 11, 10 and 9; the common leg -> GND
//
// Each reading, 0 to 1023, is mapped to a duty cycle, 0 to 255.

const int RED = 11;
const int GREEN = 10;
const int BLUE = 9;

void setup() {
  pinMode(RED, OUTPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(BLUE, OUTPUT);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: turn the three knobs to mix a color");
}

void loop() {
  analogWrite(RED, map(analogRead(A0), 0, 1023, 0, 255));
  analogWrite(GREEN, map(analogRead(A1), 0, 1023, 0, 255));
  analogWrite(BLUE, map(analogRead(A2), 0, 1023, 0, 255));
  delay(20);
}