The selectors for links in Harlowe are tw-link for markup links and link macros, and .enchanent-link for click-related macros. Additionally, links change colors on hover using the css :hover pseudoclass and upon returning to a passage after already having been visited with the .visited class. To change the color, you'll probably want to change all of these, so your selectors might look like this:
tw-story[tags="great"] tw-link, tw-story[tags="great"] .enchantment-link {
color: red;
}
tw-story[tags="great"] tw-link:hover, tw-story[tags="great"] .enchantment-link:hover {
color: pink;
}
tw-story[tags="great"] .visited {
color: violet;
}
This will make all links, regardless of how they're generated, red and pink on hover. Visited links will be violet and pink on hover.