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