Adam's picture is very nice, but I think having the "points" and "lines" colored with the same or similar colors is a bit misleading. Maybe 14 distinct colors, 7 for the points and 7 for the lines might be better. The universal cover of the picture I originally intended would be what you get if you start with a triangular lattice of circle centers on the plane, and then increase the circles' common radius until they first have triple intersections. It would resemble a picture of chain mail. Then the circles are the lines, and their intersections are the points. (Ignore the centers.) Now 7-color the "lines", and separately 7-color the "points", in a repeating way. --Dan On Oct 2, 2014, at 4:19 AM, Adam P. Goucher <apgoucher@gmx.com> wrote:
Can anyone supply a picture of Dan's construction, transplanted from T to a polygonal domain in the plane with identifications along the boundary?
Here's a picture generated from a 100-character Mathematica program:
https://twitter.com/wolframtap/status/517631202837405696
Identify discs of equal colour. Large discs represent lines; small discs represent points. Adjacency represents incidence.