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