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)(14,19)(16,17)(20,23)(21,22)(24,25)(27,28) involution — undirected(2,4)(13,14)(15,23)(16,22)(17,19)(18,21)(20,25)(24,27)(26,28) involution — undirected(6,9)(7,12)(10,11)(13,15,18,26)(14,20,21,27)(16,25,17,24)(19,23,22,28)(6,10)(9,11)(14,21)(19,22)(20,27)(23,28) 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.