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