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