Windows includes (or can download) high-contrast themes to improve visibility and there is also a screen magnifier. Both options will be found in the Ease Of Access control panel in any modern version of Windows.
Also, if you use Google Chrome (or most other browsers) somewhere in the settings are options to use larger and/or bolder fonts, restrict minimum font sizes or even magnify pages. In Chrome, it's under Settings and the scroll down to Appearance. Other browsers, I can't say exactly but it's in there somewhere. Chrome also has an extension called Zoom+ that acts like a magnifying glass.
Also in Chrome, there is an extension called
FontSize Changer, that not only changes the size of fonts but also the colors. I tried it, it works on TFL. It works page by page, so it won't change other pages. Unfortunately, it's not persistent, so you have to set it every time you visit, but that only takes a couple of seconds.