How to change underline color in Pages

On my Mac, command-t brings up the font window. You can change underline color and style there.

Here is how you change the link color, and once you do, it is wise to make a new character style from it. The follow steps were performed in Pages 11.0 on macOS 11.2.3, but work in earlier versions too:

1. Select the linked Text
2. Press ⌘+T to show the Fonts panel
3. Click the second (from the left) Toolbar item (underline)
   1. Click None
   2. Click Color and select your new link color
   3. Click Single (and your link is now the new color)
4. Dismiss the Fonts Panel
5. Create a new character style (e.g. green link)