What settings did you change? For example, on the Options page, you can change the default link colors without affecting other colors on pages:

Some users have better luck with "Never" in the lower left drop-down.

"Always" is the only setting that changes the link colors. Unfortunately, graphics are lost with that setting. There may be more than graphics, but that was the first thing that was apparent.

Right, don't use "Always" for the override setting if you want websites to look halfway decent.

The problem most likely is that websites you use have assigned their own link colors. The link colors set in the Colors dialog are the default colors used when sites do not set them. In order to override just link colors without ruining all colors, you'll need to use an add-on.

Were you able to find anything on the Add-ons site? When I search for link color this was the most obvious match, but I haven't tested it myself.

https://addons.mozilla.org/firefox/addon/visited-link-enabler/

That worked - thanks! I previously used the (legacy) extension "Visited" and selected the "Find a Replacement" option. It didn't find anything relevant and I didn't go much further at that point since it was giving irrelevant results and stopped at that point. It should have found "visitedlinksenabler" which does exactly what I wanted. I only needed to reset the "Override the colors specified by the page with your selections above" from "Always" to "Never" and it did the job perfectly. Thanks again or your assistance!

Sorry that "Find a replacement" didn't work better. I think the lists were created last October-November based on what was available at the time, and they might not have been updated as new extensions were released. (This one you're using now was made compatible in December.)