I don't think it's cut, I think it's burned then colored with a pen.
Skye is right. I burned the pattern on the blanks with a laser engraver and then colored it in with sharpie markers. My earlier (and unsuccessful) attempts at this pen were with individual segments of different woods. I discovered that separate pieces with that degree of interlock around that tight a radius are practically impossible to get together. So, I cheated.
But, it was definitely a learning experience (both in drawing the tesselation and in operating the engraver). If I make another, I'll do some things differently. For now, though, I think I'll go back to segmentations/inlays.
Regards,
Eric