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