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