Hands are typically an excellent gray reference for photography, ensuring that the captured photos represent the color accurately given the photographer’s platform constraints. Hands also help the human brain correct for variations in lighting, color profiles, monitor calibration, and so on. Showing the dye color on skin ensures the highest fidelity conveyance of the hue to the reader possible without control over how it’s viewed. Other examples of the pigment’s use would be abstract and “just another blue”; by showing in this way, it’s possible to see that it’s an uncommon and high-key blue.

It’s also extremely unusual to see a skin-safe saturated dye in this shade; most powdered sources of blue and white, which would necessarily be blended to reach these shade, would be highly toxic. So, for pigment historians and aficionados, these photographs are eerie and compelling. This is what working with pigment used to be like, before we understood how much of it was toxic and deadly to the people working with and wearing it. You could just dip your hands in the forbidden color and admire them. It’s very cool to see and I’m glad they used hands as the focus.

(There may also be cultural reasons why the dye is shown here on skin; I haven’t yet studied mesoamerican cultures and body painting, but others who are more familiar should chime in.)