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