Most Nikonians will say you don't need color filters (balance, compensation, conversion) on the D100. I find that I use them. Maybe I just can't get film out of my system. I wish I had thought of Bob's trick, using a blue card to get a warming effect. Bob, that was cool. I can't wait to get out and fool with that one.
Maybe this will help you on white balance, maybe not.
Let's say you are going to use some fill flash outside in the shade, and you want to warm the shot up. With film, you screw on an 81A and maybe cover your flash with an amber gel. On the D100, you adjust the white balance. But how? The answer Nikon gives is a set of cryptic icons for the light conditions in which you are shooting (see me scratching my head). What I do is leave my D100 in the flash setting no WB compensation. Why? Because then it is expecting ambient light at 5400 K, just like daylight balanced film. Now, I know what filter to use. It's just like shooting with daylight film.
Of course, I could just warm the light by setting some compensation, that's cheaper than B+W. Or like Bob said, I could ignore the color until I process the shot in C3, but I'm of the school that says you should get the shot as close as possible with the camera. Also, I like to see the effect of the filter on the shot. I look at the scene with and without the filter. The view you see through the viewfinder doesn't change when you dial up WB compensation or change settings.
Note: Don't put a filter on with the camera in Auto white balance. The D100 compensates for the filter and cancels it out. I had a good laugh at myself when I figured that out.
Somewhere on this forum is a white balance table for the D100. I have it lamenated in my bag. It will give you the WB settings translatted in to degrees Kelvin. I would have prefered that Nikon used WB that was graduated in degrees Kelvin, or mired for that matter, but WB gives you another dimension that you don't have with film. It's like changing film in the middle of the roll without a lightbox.
Inside with balanced fill flash or without flash I set WB to incandescant with no compensation (3000 K).