GASで選択中のセルの背景色をすべて別の色に置換する方法

function onOpen() {
  const ui = SpreadsheetApp.getUi()
  const menu = ui.createMenu('GAS')
  menu.addItem('セルの背景色を現在指定している背景色から変更', 'replaceCellColor')
  menu.addToUi()
}

function showPrompt(backgroundColor) {
  const ui = SpreadsheetApp.getUi()
  const title = '背景色を入力してください'
  const prompt = `${backgroundColor} から変更する背景色を入力してください。\n例) #ffff00 or yellow`
  return ui.prompt(title, prompt, ui.ButtonSet.OK_CANCEL).getResponseText()
}

function replaceCellColor() {
  const sheet = SpreadsheetApp.getActiveSheet()
  const selection = sheet.getSelection()
  const currentCell = selection.getCurrentCell()
  const currentCellBackground = currentCell.getBackground()
  const newBackgroundColor = showPrompt(currentCellBackground)
  const range = sheet.getRange(2, 1, sheet.getLastRow() - 1, sheet.getLastColumn())
  for (let row = 1; row <= range.getNumRows(); row++) {
    for (let col = 1; col <= range.getNumColumns(); col++) {
      const cell = range.getCell(row, col);
      const cellBackground = cell.getBackground()
      if (cellBackground === currentCellBackground) {
        cell.setBackground(newBackgroundColor)
      }
    }
  }
}