Sharpie enhanced Natural PLA test prints.
I colored the PLA with different sharpies in 6in segments alternating with uncolored segments.
Going from left to right:
purple. Just barely visible. Single shell. Not thick enough to get good color.
the end of the purple fading to natural then blue. The blue stains PLA very nicely. Double shell.
end of the blue, uncolored, then purple coloring only one side of the filament.
half blue, uncolored, full orange, uncolored, full light blue.
Conclusions: sharpie coloring works well. Color is more visible when doing more ink (obviously) or with a double shell. Darker colors show up better.
I have not tried striping or mixing colors. That’s for next time.