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