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