Walnut's heartwood is quite popular for its dark brown coloration, providing a slightly "chic" appearance without feeling like it's not "grounded." The sapwood features a dark blonde color. We do believe that the wide range of photos we've offered here properly demonstrates the range you should expect. Rarely does sapwood end up being more than 10% of the butcher block. I would say that it *never* exceeds 20%.
When it comes to endurance, walnut is a happy medium between cherry and maple (though all three are perfectly durable options!). Walnut has been increasing in popularity over the past decade for its appearance. It was once the case that non-domestic woods were preferred if a home owner wanted to add a little something to their home. This was kind of complicated because (1) these trees might be taken from national forests (2) the labor used in these practices but not be considered ethical (3) the trees might have been endangered (4) the import taxes could be quite high.
To my mind, walnut offered an alternative that helped all of these issues simply because it's from North America. It's like people collectively turned their heads away from non-domestic woods and went, "hey?! What's that beautiful wood over there? Walnut? And it's been here the whole time?"