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