MC,

Only just got round to reading this thread and I may be able to help.

A few years ago i built a Shumatech DRO system which uses red LED's but in bright light you see all the variation on the led display so a 6 looks a lot like an 8.

Some one posted a link to some red film that once put over the display made it clearer.

As I couldn't get any of this film, it was US sourced I tried using some clear OHP inkjet projection film printed solid red and it worked.

Perhaps given the price of OHP film being low you could experiment with various colours ??