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