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