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