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