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