Bruce-
While I'm putting the little paddlewheels in my gauges, I hooked up the 10V battery with one new LED installed in the volt gauge. It was quite bright, so I took it out, and dug up the green Sharpie and gave the chips on the bulb a bit of green and reinstalled. After I hooked up the battery, I turned the room light off, and lo-and-behold: green light! It was still a bright green, but I don't mind, because the marker took some of the brightness off, and since I won't be using all LEDs, I think it'll come out fine. The gauges will now have a traditional green glow. I'm looking forward to being able to read both tachys this summer, and not having to change the bulbs every year.
Since I don't have some of the weaker LEDs, I will continue to use the incandescent bulbs for the turn indicators, high-beam, etc.