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