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