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