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