An Arduino with a potentiometer communicates back and forth with a HSB selector running in p5

Serial_HSBStrip.ino

// Adafruit NeoPixel - Version: Latest 
#include <Adafruit_NeoPixel.h>

#ifdef __AVR__
  #include <avr/power.h>
#endif

//set out signal pin
#define PIN 9

Adafruit_NeoPixel strip = Adafruit_NeoPixel(5, PIN, NEO_GRB + NEO_KHZ800);

int potPin = 0;
bool grammar = 0;

int serialH = 0;
int serialS = 0;
int serialB = 0;

bool update = true;

void setup() {
  //start the strip
  strip.begin();
  //initialize all pixels to 'off'
  strip.show();
  
  Serial.begin(9600);
}

void loop() {
  //SERIAL IN ------------------------------------
    if (Serial.available() > 0){
      int inByte = Serial.read(); //Read in value
      if(inByte > 0 && inByte <= 200){ // (0-200] HUE
        serialH = inByte;
        update = true;
      }else if(inByte > 200 && inByte <= 230){ // (200 - 230] SATURATION
        serialS = inByte - 200;
        update = true;
      }else if(inByte > 230 && inByte <=255){ // (230 - 255] BRIGHTNESS
        serialB = inByte - 230;
        update = true;
      }else{
        update = false;
      }
      
    }
  //----------------------------------------------
  
  int ledNum = map(analogRead(potPin),0,1010,0,5); //Read map the potentiometer to number of LED's shown
  
  if(ledNum == 1){ // Decide if we need an 's for the LED label
    grammar = 0;
  }else{
    grammar = 1;
  }
  
  int pixelH = map(serialH, 0, 200, 0, 65536); //map the incoming values from p5 to the values the Neopixel library needs
  int pixelS = map(serialS, 0, 29, 0, 255);
  int pixelB = map(serialB, 0, 24, 0, 100);
  
  if (update){ // If the values have changed, update the strip
    for(uint16_t i=0; i<strip.numPixels(); i++){ //first wipe the strip
      strip.setPixelColor(i,0,0,0);
    }
    for(uint16_t i=0; i<ledNum; i++){
      strip.setPixelColor(i,strip.ColorHSV(pixelH, pixelS, pixelB)); //Then change the LED colors for the correct number of LED's
      strip.show();
    }
  };
  
  //SERIAL OUT -----------------------------------
    Serial.println(String(ledNum) + " " + String(grammar) + " " + String(pixelH) + " " + String(pixelS) + " " + String(pixelB)); //Serial out the values to p5, last 3 are for debug.
  //----------------------------------------------
}

SerialHSB.js

var serial; //variable to hold an instance of the serial port library
var portName = 'COM3'; //fill in with YOUR port
var data = [0,1];
var numLED = 0;

function setup() {
  createCanvas(400, 300);
  textSize(15);

  hSlider = createSlider(0, 100, 0);
  hSlider.position(20, 20);
  hSlider.style('width', '320px');
  
  sSlider = createSlider(0, 255, 240);
  sSlider.position(20, 50);
  sSlider.style('width', '320px');
  
  bSlider = createSlider(0, 100, 50);
  bSlider.position(20, 80);
  bSlider.style('width', '320px');
  
  serial = new p5.SerialPort(); //a new instance of serial port library

  //set up events for serial communication
  serial.on('connected', serverConnected);
  serial.on('open', portOpen);
  serial.on('data', serialEvent);
  serial.on('error', serialError);
  serial.on('close', portClose);

  //open our serial port
  serial.open(portName);
}

function draw() {
  //numLED = data[1];
  background('white');
  textSize(14);
  text('H', hSlider.x * 2 + hSlider.width, 35);
  text('S', sSlider.x * 2 + sSlider.width, 65);
  text('B', bSlider.x * 2 + bSlider.width, 95);
  
  colorMode(HSB,100);
  
  fill(hSlider.value(),sSlider.value(),bSlider.value());
  noStroke();
  rect(20,120,360,160);
  
  if (bSlider.value() < 75 || sSlider.value() < 125){
    fill(0,0,255);
  }else {
    fill(0,0,0);
  }
  textAlign(CENTER);
  textSize(40);
  var message;
  if (data[1] == 1){
    message = " LEDs"
  }else{
    message = " LED"
  };
  text(String(data[0]) + message, width/2, 215);
  fill(0,0,0);
  //console.log(String(data[0])+ " " + String(data[1]));
  
  //serial.write(hSlider.value() + " " + sSlider.value() + " " + bSlider.value());
  
  hSerial = Math.floor(map(hSlider.value(), 0, 100, 0, 200));
  sSerial = Math.floor(201+ map(sSlider.value(), 0, 255, 0, 29));
  bSerial = Math.floor(231+ map(bSlider.value(), 0, 100, 0, 24));
  console.log("p5 Hue: " + hSerial + " Saturation: " + sSerial + " Brightness: " + bSerial);
              
  serial.write(hSerial);
  
  serial.write(sSerial);
  
  serial.write(bSerial);
  
  console.log("Arduino Hue: " + data[2] + " Saturation: " + data[3] + " Brightness: " + data[4]);
}

function serverConnected(){ console.log('connected to the server');}

function portOpen(){ console.log('the serial port opened!');}

function serialEvent(){
  var inString = serial.readLine();
  if (inString.length > 0){
    data = split(inString, " ");
  } 
}

function serialError(err){ console.log('something went wrong with the port. ' + err);}

function portClose(){ console.log('the port was closed')}