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