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