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