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