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