sketch.h

#include <Bounce2.h>

#define RED_PIN 9
#define GREEN_PIN 10
#define BLUE_PIN 11
#define RED_BUTTON_PIN 5
#define GREEN_BUTTON_PIN 3
#define BLUE_BUTTON_PIN 4
#define REMOVE_BUTTON_PIN 8

Bounce rButton = Bounce(RED_BUTTON_PIN, 5);
Bounce gButton = Bounce(GREEN_BUTTON_PIN, 5);
Bounce bButton = Bounce(BLUE_BUTTON_PIN, 5);
int r = 0, g = 0, b = 0;

void setup() {
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
  pinMode(RED_BUTTON_PIN, INPUT_PULLUP);
  pinMode(GREEN_BUTTON_PIN, INPUT_PULLUP);
  pinMode(BLUE_BUTTON_PIN, INPUT_PULLUP);
  pinMode(REMOVE_BUTTON_PIN, INPUT_PULLUP);
  Serial.begin(9600);
}

void loop() {
  r = handleColorButton(RED_PIN, &rButton, r);
  g = handleColorButton(GREEN_PIN, &gButton, g);
  b = handleColorButton(BLUE_PIN, &bButton, b);
  handleRemoveButton();
}

int handleColorButton(int colorPin, Bounce *button, int color) {

  if ((*button).update() && (*button).rose()) {
    Serial.println("+");
    color = constrain(color + 10, 0, 255);
    analogWrite(colorPin, color);
  }
  return color;
}

void handleRemoveButton() {
  if (!digitalRead(REMOVE_BUTTON_PIN)) {
    r = 0;
    g = 0;
    b = 0;
    analogWrite(RED_PIN, r);
    analogWrite(GREEN_PIN, g);
    analogWrite(BLUE_PIN, b);
  }
}