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)(15,21)(16,23)(17,28)(18,25)(19,24)(20,26)(22,27) involution — undirected(1,2)(3,4)(6,10)(11,12)(13,15,20,16)(14,21,26,23)(17,18,27,19)(22,24,28,25)(5,7,9,8)(6,11,10,12)(13,16,18,27,20,15,19,17)(14,22,24,23,26,28,25,21)(2,4)(13,17,19,15,20,27,18,16)(14,23,25,22,26,21,24,28)(5,8,9,7)(6,11,10,12)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.