As a musician and sibling to an incredible sax player (I'm only mediocre), I think the dark grout looks better. It kind of "ages" the sax so that it looks more sophisticated. Not to mention the lighter grout would've washed out all of the color, if you know what I mean. It would've been way too bright.
I really love this! Now I want to make one for at least one or two of my favorite instruments. Probably Piano and French Horn or something. WAY easier than saxophone, I don't think I have that much patience