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