I have begun tests to try and determine the best anode resistor for the IN-12B Nixie tubes that I have. I used a very nice calculator to try and determine a safe value for the tube to light up, but not to shorten the lifespan of the tube too much. According to the calculator, at 180v and trying to give the tube 1 mA (well below the max of 2.5 mA), a 10 kOhm resistor should be sufficient. When I tested it, the tube was very bright and had a little bluish glow around the orangeish pinkish number. It was difficult to photograph, but definitely there. According to some sites, it's nothing to worry too much about, and just a sign that the tubes were "ultra long life" prepared, by adding mercury to the gasses inside the tube. I'm going to try some other values of the resistor to see if I can get the tube to some sort of sweet spot where it is a good brightness. I might implement a Potentiometer in the final clock design to be able to dim the tubes at night, or I might add a photoresistor to automatically detect the dark and dim them. Or I might do neither and just get used to the brightness.