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