defines colors for specific hyperlinks

This change is in response to the hyperlinks that are barely visible.

To change that, the main stylesheet needs to be modified: https://gitlab.ethz.ch/vseth/0403-isg/libraries/npm-vseth-theme/-/issues/5

This MR sets the primary theme color for the links that shouldn't have the typical theme color so that the link color can freely be modified in npm-vseth-theme.

Additionally closes