Hi Skip . The red Tigers mine mate I scratch built the rear convoy light with help and advice of the forum ,if you want any help mate just ask . I think some were green but Im no expert.
I am sure I read somewhere that they were blue, and were convoy lights. They were only visible when the tank behind was (I think) 30 metres distant. This ensured that they kept a safe distance from each other in the dark.
I am also pretty certain that interior lights were red. The maps that they used were apparently strange colours so that they could be read in a red light.
Many tanks had both red and green or blue tail lights. They were built with a plate that could be flipped up or down depending on the use. Red would be for standard road traffic in conjunction with headlights. The green or blue were for tactical convoys and had squares built into them. Too far and you couldn't see them at all (green light doesn't carry well at night, blue even less). Depending upon how close you were the green or blue light looked like a single light or multiple lights (closer up). That's how they could do the spacing.
By the way, NATO still uses red-light maps. The colors on the map are such that nothing is in red so everything remains visible under a red-lens flashlight. Red, green and blue won't effect your night vision. Although, I'm still puzzled as to why we would use the color most visible from a distance.
There were 2 different types of convoy light used on German vehicles. One was a small rectangular box with a hinged cover. Depending on the position of the cover, different lights were visible.
The second type was a simple metal tube with 4 rectangular cutouts and a coloured glass tube, which could presumably be changed to give different colours when required.
The idea of the 4 lights of the same colour was this: If the driver of a following vehicle was too close to the tank in front he would see 4 lights. If he was too far away he would only see it as one light. If he was following at the correct distance it would appear as 2 lights.
There are tanks at Bovvy which have mountings on for the box type (known as a Notek) but I haven't seen any there with the light still present. Google might turn up some pics of it though.
The recently restored JP that does the rounds of the shows in the UK has the tubular type fitted and the glass in it seems to be a sort of blue/green colour, though I have never seen it lit. Maplins do LED's that are a turquoise colour (I think they might call them aqua, or something like that)
I built one of the tubular type for my 1/8 Panther and I was very surprised how effective it was. As I walked backwards from the rear of the tank there is a very noticable change from 4 lights to 2 and then to 1. Eventually the light vanished totally, but that was because I fell over the dog. My fault for walking backwards!
Hope this helps - it is a subject that has come up several times on various forums.