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