One of the very kind proof readers raised the issue of colour blindness and how it might relate to my topos. Originally I planned to use white lines (with various dots and dashes to distinguish lines that overlapped) but I felt they weren’t clear enough so started using a mix of white and red or green (which I used depended on the colour of the background) dashed lines.

So I have redrawn one topo in four different ways to see which is most effective.

1. Red and white dashed lines

2. White dashed lines with a black background.

3. White dashed lines.

4. White solid lines.

Thoughts welcome…