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