int channel = 0;
//R = 0
//G = 1
//B = 2

int pinR = 9;
int pinG = 10;
int pinB = 11;

int pinT = 4;

bool hasPressed = false;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(pinR, OUTPUT);
  pinMode(pinG, OUTPUT);
  pinMode(pinB, OUTPUT);
  pinMode(pinT,INPUT_PULLUP);
}

void loop() {
  // put your main code here, to run repeatedly:
  int potValue = analogRead(A0);
  float percent = potValue / 1023.0;
  
  if(channel==0) {
    analogWrite(pinR, 255*percent);
  } else if(channel==1) {
    analogWrite(pinG, 255*percent);
  } else if(channel==2) {
    analogWrite(pinB, 255*percent);
  }

  if(digitalRead(pinT)==LOW) {
    if(hasPressed==false) {
      hasPressed = true;
      channel = channel + 1;
      if(channel>2) {
        channel = 0;
      }
    }
  } else {
    hasPressed = false;
  }

}