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