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