That's surprising---by default, the color for links should be blue on
bright backgrounds. It's cyan on dark backgrounds, but cyan should be
perfectly visible on dark backgrounds. Have you performed any color
customizations?
That's my point. I haven't.
As I was saying, the shade of blue used for links should be legible by
default, and it's a bug if it's not. Can you confirm that it's cyan on
a white background, as opposed to dark blue on a white background (which
is what I see for the default on GNU/Linux)?
How do I do it?
Customize the `link' face (see the Emacs manual for details of
customization).