A half symmetry coloring is tr{∞,∞}, has two types of apeirogons, shown red and yellow here.
If the apeirogonal curvature is too large, it doesn't converge to a single ideal point, like the right image, red apeirogons below.
Coxeter diagram are shown with dotted lines for these divergent, ultraparallel mirrors.
From [∞,∞] symmetry, there are 15 small index subgroup by mirror removal and alternation.
In these images fundamental domains are alternately colored black and white, and mirrors exist on the boundaries between colors.