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