One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,12)(8,10)(9,11)(13,14)(15,17)(16,23)(18,22)(19,21)(20,27)(24,25)(26,28) involution — undirected(1,2)(3,4)(5,7,9,8)(6,10,11,12)(13,15)(14,19)(16,24)(17,22)(18,21)(20,26)(23,27)(25,28)(5,8,9,7)(6,10,11,12)(13,16,18,26)(14,20,22,24)(15,23,21,28)(17,25,19,27)(2,4)(14,15)(17,19)(20,23)(21,22)(24,28)(25,27) involution — undirected(6,11)(10,12)(13,17,18,19)(14,21,22,15)(16,25,26,27)(20,28,24,23)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.