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