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