You don't always need to match. Sometimes a complement looks good. The Ebony over Wenge that's been mentioned a couple times would do that. A black fretboard will complement anything, and the solid dark chocolate brown Wenge neck meat will complement the streaks in the Limba nicely. Plus, it would be a fairly even-toned neck that satisfies your desire for a raw wood. I've had several necks here with that construction, and they're nice. My only caveat would be that the Wenge is pretty open-grained wood, so if you have a tendency to sweat a lot, it could get grungy.