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