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