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