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