Is it possible to assign a ringtone to contact groups

[Mike JT]

Just got a Moto E and ported the contacts across with success including the groups. I have been able to assign a generic ringtone to calls, as well as ringtones for a couple of specific individuals but was wondering if its possible to assign a ringtone to a contact group (or do you have to assign the same ringtone to each of the members individually) ?

Also, is there any significance to the different coloured discs next to contacts names.