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