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