Old World technology rocks!

On the other hand, why do you want to play Fallout without colors? A lot of the enviroment relies on color scheme to tell the difference between them.
Anyway, since you are on a PC, there isn't really a native black & white theme for Windows, but this won't affect the game.
Your monitor doesn't have color controls? It's LCD or CRT? Unless it's really an old monitor you can control the colors, just access the OSD of the monitor and set the color scheme to manual, user or whatever these lines (sometimes you access the colors in a menu called "color temperature").
Then you can configure the RGB color settings to grayscale (b&w), simply put all three color controls at 0.
Hope this helps