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)(18,22)(23,27)(24,26)(25,28) involution — undirected(1,2,4,3)(7,12)(9,11)(13,15)(14,18)(16,22)(17,23)(19,21)(20,26)(24,25)(27,28)(5,7,8,12)(6,9,10,11)(15,22)(18,21)(23,24)(26,27)(6,10)(9,11)(15,23)(17,25)(18,26)(20,28)(21,27)(22,24) involution — undirected(1,3,4,2)(14,19)(18,21)(20,28)(26,27)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.