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