One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,11)(8,10)(9,12)(15,21)(16,24)(18,26)(20,27)(22,28)(23,25) involution — undirected(2,3)(5,7,8,12)(6,9,10,11)(13,14)(15,22)(16,20)(17,19)(18,23)(21,28)(24,27)(25,26)(1,2,4,3)(7,12)(9,11)(13,15)(14,18)(16,25)(17,23)(19,22)(20,28)(21,24)(26,27)(6,10)(9,11)(13,14)(15,18)(16,20)(17,19)(21,26)(22,23)(24,27)(25,28) involution — undirected(1,3,4,2)(14,19)(18,22)(20,27)(26,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.