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