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