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)(15,19)(16,25)(17,21)(18,22)(20,23)(24,27)(26,28) involution — undirected(1,2,4,3)(5,7)(6,9)(8,11)(10,12)(13,15,18,24)(14,19,22,27)(16,26,23,17)(20,21,25,28)(6,10)(7,11) involution — undirected(6,10)(9,12)(13,16,17,15,18,23,26,24)(14,20,21,27,22,25,28,19)(1,3,4,2)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.