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