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