Just chatting with my alarm guy and he has suggested our external alarm box is fitted with blue LEDs which highlight his logo to demonstrate to any nasty people that it's an active alarm box, not to advertise his company you understand - for some reason I feel this is a bit OTT - not sure I want my alarm box lighting up blue at night - I have asked if I had the option to turn it off but he says that only he can disable the lighting...so it's either off or on all the time.
WWYD - lights on all the time for extra security or a more subtle light free solution. We live in a fairly low crime area.