Dig down from station 59 on the zomp line and you hit station 59 on whatever the inverted colour is.
The party's own line becomes the worked example of Katia Grim's theory. They are at station 59 on the zomp line; if the mirror runs per-line rather than across the whole tangle, then digging straight down from where they are standing reaches another station 59, upside down, on the line whose colour is zomp's opposite on the colour wheel. She does not know which line that is.
She is confident the The Space In-Between lies between the two.
The party's current line, and the test case for the mirrored-tangle theory.