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