Rated 5 out of 5 stars

I have just installed this in both Thunderbird and Firefox and I love it. With a high resolution wide screen and 70 year old eyes even with my glasses I've been struggling to see much of the text in many windows and this has been exactly what I've needed to make using my computer a lot easier and a lot more fun!

My only additional wish would be to be able to change the contrast between the background and text in so many of the little windows that show up from time to time - dark grey backgrounds with darker grey text are very difficult to read as are light grey text with lighter grey backgrounds.

Thank you for a great add-on!

This review is for a previous version of the add-on (1.7). 

Thanks

Thank you for the kind comments. Theme Font & Size Changer was developed specifically for individuals with situations likes yours.

I'm not sure exactly what you're referring to when you speak of "the contrast between the background and text in so many of the little windows that show up from time to time". Perhaps you're talking about some of the popup windows and dialogs. If you are seeing gray against gray, it could be that you're seeing text that indicates a disabled feature, otherwise, the text should be black.
In any event, there are some solutions.

One is that you can try a different Theme for Firefox and/or Thunderbird, another is using a little snippet of code to fix the issue.

For a Firefox Theme, any of Ed Hume's Aeon themes would help. All windows and dialogs have white backgrounds with black text. Some of his Aeon themes have large, and extra large icons and buttons so that may be of additional help.

Ed Hume's Firefox themes.
https://addons.mozilla.org/en-US/firefox/user/104/

For Thunderbird, the variety for themes is very limited so you're better off with the following method.

You can add a snippet of code to Firefox and Thunderbird that will force all windows, popups, dialogs, etc to be displayed in the colors of your choosing.
The following code makes background colors white and all text black.
* {
background-color: #FFFFFF !important;
color: #000000 !important;
}

This can be added to your userChrome.css, or you can use the Stylish add-on.
If you'd like help implementing this, feel free to contact me at the following.
KenSaunders at AccessFirefox .org