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