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