I think it would depend on what "image" you preferred to project.
Blue, purple, yellow, maybe green too- "oily diesel"
Blue, red, yellow- "flame"
White may highlight, but if not dim, Id expect it to look like "light leakage".
I've been thinking of the easiest way to incorporate light into an assembly, but haven't had that many stock electronic fan driven locomotive smoke units in my hands too know the variations or internal placements well, but think if the unit uses a tube between the opening, & the models stack, and is replaced with a glass tube & JB weld, it would provide a heat resistant, but clear tube for the light to pass through. I have done this with brass tube for custom smoke unit "stack extensions"/"exhaust manifolds".
