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