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