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