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