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