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