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