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