For really tidy labelling how about using the Neutrik transparent coding ring to go on the XLR connector, it will fit a 6mm label underneath. There are also coloured bands available for the connectors.
www.neutrik.com
Neutrik are excellent at coming up with inventive ways to take your money for what seems like a simple component.
XXCR
Transparent coding ring which allows an individual customized labeling, branding, coding etc.Just place an individual coloured and or lettered paper or tape (eg. Brothers) inside the ring.Box of 100 pcs.

Neutrik are excellent at coming up with inventive ways to take your money for what seems like a simple component.