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