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