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