I saw this a few days ago, and looked through the comments until I found that the gray wood was called Bog Oak. I'd never heard of it, so googled it. It's very interesting, also very expensive. Apparently most of it comes from Russia and Ireland. It's been buried in wet bogs for many years and gets darker gray with time.Pretty neat, Theo. Is that Wenge and Beech?
I saw some color charts, and most of the bog wood sold is between 1000 and 5000 years old. The older the darker. The joint experiment looks to be about 1000 year old Bog Oak.