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