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