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