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