How does the backlight work on these LCDs? Is it a pair of coloured leds? I've got a backlight from a broken LCD (the backlight still works) but it looks different to the nuelectronics shield backlight, the busted one has a single anode/cathode pair of pins that are on a white bit of plastic that is the base, the nuelectronics has 2 pairs of A/K and look like they go into to little square lumps of plastic (like leds) .
They are normally tiny surface mount LEDs on the bottom of the display with a diffuser... They are not easy to replace.
red for protecting night vision as bright green/blue light is a pita for astronomy
Yes, red is best for astronomy... 
Just out of interest, what is the astronomy project? I haven't seen many around...
Regards,
Mowcius