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