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