When I'm creating a new website, I have a lot of decisions to make about the theme. I am not a designer, so I usually just find a decent starter theme and make some small changes.
On a recent project - The Democracy Habit - I needed to decide what color to use for text links.
I want to make my sites as accessible as possible, so I started with that as a guideline, then looked for recommendations based on solid research about both accessibility and usability.
I often focus on academic sites for searches like this by adding "site:edu" to my search terms. Most universities have a strong commitment to accessibility in design, and they often use - and cite - solid research to support their choices.
I found the UC Berkeley Digital Accessibility page on Links. They recommend underlining links - as we did back in the old days of early HTML - and recommend blue as the best color for links to avoid problems for site visitors with color blindness.
I followed that guidance and implemented links at The Democracy Habit using blue text and underlines, and I think that works well.
It's always surprising to me to visit a site that has links that are indistinguishable from regular text. For example, one of my favorite bloggers, John Scalzi, uses bold text for links, with no underline or color difference, and I can never tell what's a link and what's just bolded for emphasis.
I'm pleased with my blue links; it's reassuring to have solid research supporting design choices.