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