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