Bobvalk,
I believe the blueish color you see at night is because of the "color" of the LEDs that are used to illuminate the face of the Display at night.
"White" LEDs are not always "pure white light" (and that's an oxymoron if I've ever heard one). They are like fluorescent light bulbs in that they can have a "tint" to them. As you are aware, some fluorescent bulbs produce a blueish light, some a yellowish light, and some are said to be "full spectrum" meaning that their "tint" includes "all" of the color spectrum in a "balanced" ratio - like sunlight. Truly "white" light includes all of the colors of light, so it is really a combination of all the color spectrum - it isn't "pure" at all (that's the oxymoron, above).
LCDs don't "emit" light, they just reflect the light that hits their surface or passes through them. To see a LCD in the dark it has to have "backlighting," or "lights" of some sort that hit the surface or pass through the surface of the LCD. Check out this link; notice the colors of the LCDs, whether they are STN, FSTN, "+" or "-", and the color of the backlighting. Note, too, if they are "transflective" or "transmissive":
http://www.newhavendisplay.com/lcd-graphic-128-x-64-c-21_96.html.
I believe the LCD used in the GL1800C Display is a custom FSTN- display with "white" LED backlighting. But the tint of the LEDs is "blue," so, at night, the light reflected off of the LCD and into your eyes appears blue.
Of course, I could be wrong.
Bill
