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