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