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