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