I bought a few string nut blanks in what is called ‘Vintage Bone” color for the shop at one point to try on my classical guitar build. I loved the outcome so much that since then I have recommended this style bone to lots of customers as an alternative to the standard white bone. The only difference I have been able to figure out is that what we call standard bone is actually bleached white, and the vintage bone is unbleached. They both seem to cut the same and exhibit the same hardness for good tone transfer.
Either way, once the vintage bone is sanded and polished, it really comes out incredibly classic looking, almost like fossilized ivory or even marble. It goes very well on acoustic guitars or any guitar that has more of a cream or aged looking binding. For guitars with a whiter binding or more modern body style, I think the standard bleached bone looks better.
Here are a few shots i took of a Gibson 335 I worked on sometime in 2009 and one picture of a classical guitar I did just this week using the vintage bone. In these shots you can also see what the blank looks like at the start and the finished product. Starting with the pre-cut blanks helps but there is still alot of shaping involved to get each string nut to fit just right. cutting the string slots at the proper location and depth, and then final shaping, sanding and buffing.