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