If you get your LED characters perfectly lined up you can do this trick.

Put in a second Image_Map. Use the 8 to make the unlit segments look black against a dark gray background, and then the other Image_Map lights up some of those in red.

In my case, the number 1 is not lined up properly. Make sure all your digits line up.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)