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