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