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