"color separation filters" are dichroic (reflective) thingies that are made using thin-film metal deposition on glass.
CSF are superior to theatrical and gel filters in terms of accuracy and stability, but as I understand it, this project doesn't need accuracy.
Typically RGB, CSF's are used to isolate out narrow bands of spectrum. I think they're also used in LCD monitors, but I might be wrong here.
In tri-color separation photography for dye-transfer printing, they use Wratten #25 (red), #58 (green) and #47 (blue) filters. These might well be the ones suitable for this project.
For the techy part of the project, the colours form three points of a triangle within the CIE chromaticity thingy below. Colours outside of the triangle are un-resolvable.
**broken link removed**
You can use a PC and its colour monitor to test the instrument with, just create the colours by entering the RGB values in something like PaintShop or Adobe watsitcalled.