Usually the instrument panel color is determined by the silkscreen printing on the plastic sheets of the instrument panel inserts. It's not usually a filter over the light bulbs. You would have to make/find alternate instrument panel inserts, not a trivial task.

Something to keep in mind is that the empeg's VFD is simply a different kind of light than the instrument panel lights, and in most cases there is little you can do to make it match exactly. Instrument panel lights are diffuse, shining through milky plastic sheeting with flat areas of color. The silkscreen printing on the plastic sheet determines the shape of the numbers and symbols.

The empeg VFD, on the other hand, is direct-view fluorescent pixels, and it's not diffused at all. This gives the light a completely different quality. So there's little chance of you being able to match its appearance to your dash exactly.

The best you can hope for is to get in the same neighborhood (greenish dash=green empeg, bluish dash=blue empeg).