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)(16,20)(18,23)(19,21)(22,26)(24,27)(25,28) involution — undirected(2,3)(6,9)(10,12) involution — undirected(1,2,4,3)(13,15,17,14,19,23,18,21)(16,22,26,20,25,27,24,28)(1,3,4,2)(13,16,19,25)(14,20,21,28)(15,22,23,27)(17,26,18,24)(5,7,8,11)(6,10,9,12)(13,17,19,18)(14,15,21,23)(16,24,25,26)(20,27,28,22)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.