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)(13,14)(15,16)(17,26)(18,21)(19,24)(20,23)(22,28)(25,27) involution — undirected(5,6)(7,11)(8,10)(9,12)(13,15,18,23)(14,19,21,25)(16,22,20,26)(17,27,28,24)(2,4)(5,7,8,12)(6,9,10,11)(13,15)(14,20)(16,21)(17,24)(18,23)(19,22)(25,26)(27,28)(7,12)(9,11)(13,16,18,20)(14,15,21,23)(17,19,28,25)(22,27,26,24)(6,10)(9,11)(14,21)(15,23)(22,26)(24,27) 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.