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)(15,18)(16,19)(17,24)(20,22)(21,27)(23,26)(25,28) involution — undirected(1,2)(3,4)(6,10)(11,12)(13,15,20,16)(14,18,22,19)(17,25,26,21)(23,27,24,28)(5,7,9,8)(6,11,10,12)(13,16,19,14,20,15,18,22)(17,24,28,21,26,23,27,25)(2,4)(5,8,9,7)(6,12,10,11)(13,17,19,28,20,26,18,27)(14,21,15,23,22,25,16,24)(6,10)(11,12)(17,26)(21,25)(23,24)(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.