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