One vertex per element, one color per generator, with an edge from x to x·s.
(2,3)(5,6)(7,9)(8,10)(11,12)(13,14)(15,19)(16,22)(17,23)(18,27)(20,25)(21,24)(26,28) involution — undirected(1,2,4,3)(5,7,8,11)(6,9,10,12)(13,15)(14,19)(16,26)(17,25)(18,24)(20,23)(21,27)(22,28)(6,10)(9,12)(13,15)(14,20)(16,26)(17,25)(18,24)(19,23)(21,22)(27,28) involution — undirected(1,3,4,2)(13,15)(14,21)(16,24)(17,25)(18,26)(19,27)(20,22)(23,28)(13,16,17,18)(14,22,23,27)(15,24,25,26)(19,21,20,28)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.