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