One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,11)(8,9)(10,12)(13,14,19,22,17,20,18,21)(15,23,26,27,24,16,25,28)(1,2)(3,4)(6,9)(10,11)(13,15,19,26,17,24,18,25)(14,16,22,28,20,23,21,27)(2,4)(5,7)(6,10)(8,12)(9,11)(13,16)(14,15)(17,23)(18,28)(19,27)(20,24)(21,26)(22,25) involution — undirected(7,12)(10,11)(13,14,17,20)(15,16,24,23)(18,21,19,22)(25,27,26,28)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.