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