Re: SD posted this Mayones on their Facebook page.
Normally the black would be in the deeper parts of the grain. This can be achieved by staining the whole body black, sanding it down so that it only remains in the grain, then staining again with the "main" color.
In this case, the black is on the raised areas, and the blue is in the deep grain. This is much more difficult. You can't use the technique above, because the black dye will just obscure all the blue dye.
I can think of two ways to do this:
1. Do the blue stain, then seal it with a couple coats of urethane or similar clear finish. Next, sand gently to remove the blue and the clear sealing coat from the raised areas only. Apply the black stain - it will only stick to the areas where you sanded off the clear. NOTE: for this to work properly, you need to use water-based stain and oil-based clear, or vice versa.
2. Do the blue stain. VERY CAREFULLY apply the black stain only to the raised areas.
Of the two, I would probably do the first one - it's more time consuming but also far less prone to mistakes.