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