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