The green and red wires both go to the earth terminal - which will link to pin 3 in the socket. Your modem will only connect to pins 2 and 5 so it won't be a problem. It's not the ring wire.
More recent versions of the socket dispensed with the earth terminal completely. There is every chance that your 'earth' doesn't actually connect to anything that's earthed. The red and green wires may just be attached to the earth terminal to keep them tidy.
The box terminal will probably be where the line comes into the property from the outside and it will then have the red/green/orange/blue cable connecting to the master socket.
My phone line comes into the house via an even older connection box - a GPO 20/4 (installed in 1955) seen here
- and it doesn't mean I can't get an excellent broadband speed;
> DS Channel1 DS Channel0 US Channel1 US Channel0
> Speed (kbps): 0 79999 0 20000
Edited by caffn8me (Sat 16-May-15 03:30:04)