If you use markdown style links the css attributes for changing external link color won’t work because it thinks that all markdown style links are external.
There’s that little icon at the end of external links, which is helpful, but it’s not obvious enough for me because of who I am as a person.
This does not work in reading mode, which is on purpose because I only want it in editing mode. This also doesn’t pick up when you’re editing/creating a link and that’s fine by me as well.
.markdown-source-view.mod-cm6 .cm-link:has(~ .external-link) .cm-underline {
/* Your styles here */
color: #B0F89A;
}