old-monorepo/Dashboard/src/App.tsx

import React from "react";
import SerialPort from "serialport";
import { remote } from "electron";
import Knob from "../assets/Knob.svg";

const App = () => {
  // https://www.electronjs.org/docs/api/system-preferences#systempreferencesgetcolorcolor-windows-macos
  console.log(remote.systemPreferences.getColor("active-border")); // border
  // https://www.electronjs.org/docs/api/system-preferences#systempreferencesgetaccentcolor-windows-macos
  console.log(remote.systemPreferences.getAccentColor()); // accent color

  const port = new SerialPort("COM5", {
    baudRate: 9600,
    autoOpen: false,
  });
  const handler = () => {
    // eslint-disable-next-line
    port.write('off', (err) => {
      if (err) {
        return console.log("Error on write: ", err.message);
      }
      console.log("message written");
    });
  };

  return (
    <div>
      <img src={Knob} alt="Knob" height="180px" />

      <button
        type="button"
        onClick={() => {
          port.open();
        }}
      >
        open
      </button>
      <button
        type="button"
        onClick={() => {
          port.close();
        }}
      >
        close
      </button>
      <button type="button" onClick={handler}>send</button>
      <button
        type="button"
        onClick={() => {
          const list = SerialPort.list();
          list.then((arg) => { console.log(arg); });
        }}
      >
        list
      </button>

    </div>
  );
};

export default App;