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)(15,24)(16,21)(17,20)(18,22)(19,23)(25,28)(26,27) involution — undirected(5,7,9,8)(6,10,12,11)(13,15)(14,20)(16,26)(17,18)(19,25)(21,28)(22,24)(23,27)(2,4)(5,7,9,8)(6,11,12,10)(13,16)(14,21)(18,19)(22,23)(25,26)(27,28)(5,8,9,7)(6,10,12,11)(13,17)(14,20)(15,18)(16,25)(19,26)(21,28)(22,24)(23,27)(15,25)(16,19)(17,26)(20,27)(21,23)(24,28) 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.