It is not possible to connect to blue.cs.sonoma.edu over the Apple File Protocol (AFP) due to how the campus Firewalls are configured. If you want to mount a share using AFP, you can still do it over an SSH tunnel.
In a terminal where you have access to SSH, do:
sudo ssh blue.cs.sonoma.edu -l yourUsername -L 22:127.0.0.1:548
Then, you can use the following destination as the endpoint to mount the share via AFP:
afp://localhost:22
To disconnect, unmount the share that you mounted and then type exit in the terminal where you created the ssh tunnel.