[spuz]

If you don't want to install a 3rd party extension (maybe it seems like too much of a risk for such a frivolous purpose), then you can make your own. Just download hacker95.css and create a file called manifest.json in the same directory with these contents:

  {
    "name": "Hacker News 95 Extension",
    "version": "1.0",
    "description": "Hacker News 95 Extension",
    "permissions": ["activeTab"],
    "content_scripts": [
      {
        "matches": ["https://news.ycombinator.com/*"],
        "css": ["hacker95.css"]
      }
    ],
    "manifest_version": 2
  }

Then in your Chrome Extensions settings, find the option to "Load unpacked extension" and point it to your directory.