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)(14,19)(15,22)(16,17)(20,28)(21,26)(23,27) involution — undirected(5,7,8,11)(6,9,10,12)(13,14)(15,23)(16,19)(17,26)(18,21)(20,22)(24,28)(25,27)(2,4)(13,15,17,25,18,22,16,24)(14,20,19,27,21,23,26,28)(6,10)(9,12)(13,16,18,17)(14,19,21,26)(15,24,22,25)(20,27,23,28)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.