Visually checking font-size on the page.

console.js

(() => {
  document.querySelectorAll('*').forEach(el => {
    const hasDirectText = Array.from(el.childNodes).some(
      node => node.nodeType === Node.TEXT_NODE && node.textContent.trim().length > 0
    )
    if (hasDirectText) {
      const size = window.getComputedStyle(el).fontSize
      if (size === '16px') {
        el.style.backgroundColor = 'red'
      } else if (size === '15px') {
        el.style.backgroundColor = 'green'
      } else if (size === '14px') {
        el.style.backgroundColor = 'blue'
      } else {
        el.style.backgroundColor = 'yellow'
      }
    }
  })
})()