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