A tip from model railroading:
If the object is going to be looked at mostly in daylight, then make the color match in daylight.
If the object is going to be looked at mostly in artificial light, then make the color match in that light.
Your eyes fool you in such matters. You can see it in the way the surface of the rifle appears slightly different according to whether you place it on the highly reflective brown table top, or on matt white paper. You think it looks the same in both cases, but the camera shows up the difference.
Furthermore, a slightly darker streak on a medium color wood surface is less obtrusive than a lighter streak on the same surface. But it will be very fiddly to darken just those fillings. The oiled wood may take up an oil or spirit based stain much easier than the epoxy-sealed filling. If you let the stain flow onto the surrounding wood, you may therefore exaggerate the color difference, instead of blending it out. Go very, very carefully!
Good luck!![]()