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