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